Young Joe McClaine, the adopted 9 year-old son of Professor McClaine, little realises how important his role will be when his father introduces his latest invention to World Intelligence Network agent Sam Loover. Dubbed the Brain Impulse Galvanoscope Record and Transfer, big rat for short, it can record the brain pattern of any individual and plant their knowledge and skills into another person. Shane Weston, Deputy Head of win, sees Joe as a most unusual secret agent. After all, who would ever suspect a child of being a top-notch secret agent. He outlines a typical mission in which Joe is given the brain pattern of a Russian pilot and is sent with Mac to the Soviet Union to steal the most advanced fighter plane in the world, the MiG 242. No one believes the poor security officer who reports the theft of the MiG and Joe's ability to out-manoeuvre the MiG interceptors puts further doubt on the officer's claim. Professor McClaine fails to see the simplicity or humour in Weston's scheme and a heated shouting match ensues until the Professor finally agrees that the potentials are enormous for win's Most Special Agent.

win decides it's a mission for Joe when a ruthless gun runner named Colletti murders one of their agents. Receiving information that Colletti will hijack a delivery of arms that very night, the plan is to locate the villain's hide-out by planting little Joe in one of the crates. Armed with the brain pattern of win's top agent, Joe eventually finds himself in a remote barn which hides the entrance to a vast underground complex. While investigating, Joe sets off a hidden electronic alarm and is captured. At first Colletti is amused by Joe who has lost his glasses but the gun runner decides the boy knows too much and orders his men to kill him. While driving Joe to a cliff, where he will be thrown off, the boy escapes from the car boot but not before planting a transmitter. While Mac and Sam follow the signal back to the complex, Joe makes his way back to Colletti's office to retrieve his glasses and a fierce fight ensues.

Shane Weston is suspicous when the flight manifests of two crashed airliners list two brilliant electronics experts. Mac is asked to act as bait with Joe his secret bodyguard, programmed with the brain pattern of a top U.S. Air Force test pilot. Sure enough, the duo are tailed from the cottage to the airport and on to their Athens-bound plane by Kramer, a ruthless international kidnapper. Both the pilot and the co-pilot are drugged and Mac is forced at gun-point into an escape capsule. Believing the plane to be doomed, the kidnappers are picked up by a motor launch which will take them to an enemy submarine. They are surprised when the jet-liner dives out of the blue. As the Navy moves in on the enemy submarine, the plane (piloted by Joe) holds the launch at bay by diving between the two boats.

Mac is puzzled when win requests that he record the brain patterns of world-famous pianist Igor Sladek until he learns that the man is, in fact, a top agent for the organisation operating under cover. When Sladek's cover is blown and he faces arrest during a tour of Eastern Europe, Mac and Joe are sent to the studio where the pianist is to give a live performance. Joe succeeds in getting permission to turn the music for Sladek who asks that the baffle screens be shifted slightly. Now he and Joe are out of sight of those watching them. Donning his glasses, Joe activates his programmed brain patterns of Sladek and switches places with the maestro without missing a note. Mac smuggles Sladek through the border, as Joe continues giving the concert, unknown to the enemy. Can he also escape without being discovered?

When world famous writer Maurice Estoral faces a brain operation, Mac fears for his life at the inexperienced hands of Dr Blakemore. Initially Estoral was to be operated on by the eminent surgeon Emil Kados but the doctor was gravely injured in a plane crash. Mac and Joe secretly visit Kados in intensive care and record his brain patterns which are to be transferred to Joe. Since the hospital would obviously not allow a 9 year-old child to operate, Mac receives the brain pattern of a highly trained win agent. As Estoral is wheeled into the operating theatre, Mac makes a dramatic move. Holding the staff at gun-point, Joe begins the delicate surgery. The operation is a triumphant success — but how to keep Joe's identity a secret?

Joe and Mac arrive in Porto Guavan, ostensibly on a fishing trip but in reality on a top secret win mission to avert an international incident. An advanced two-man submarine was crippled during a test by an inrush of water into the missile tubes. Though the crew had been rescued, the craft drifted into forbidden waters and now lies in Porto Guavan territory. The McClaines charter a boat and while Joe dives on the sub, he becomes trapped. The Porto Guavan Coast Guard, unable to locate Joe, arrest Mac and the boat captain, charging them with murder. Joe succeeds in freeing himself and getting the submarine away from the forbidden area. Now he must rescue his father and the boatman from jail.

While mining Uranium 534, a geologist and two young physicists are trapped in an old silver mine. The geologist is Sam Loover's father and the win agent fears that he will die without the regular injections of serum he requires. The brain pattern of a leading underground explorer is transferred to Joe. Using exact directions supplied by Sam, Joe still finds the going dangerous. Crumbling footholes, sheer rock faces which have to be scaled by rope and breathtaking drops face the young secret agent as he struggles to reach the three men.

Mac and Joe are assigned to track down the source of counterfeit notes that are flooding the world market. Using the brain patterns of a World Bank President, Joe establishes that the forgeries were printed within the past two weeks from plates that were reported destroyed. A lead on the forgers is discovered when the Reverend of a supposedly haunted church pays counterfeit notes into the bank. Mac and Joe pay a call on Reverend Joseph Shepherd and eventually get the nervous man to admit that he is being blackmailed. The crooks are holding his verger hostage to use the church crypt as their secret workshop. A plan is cooked up to dress Joe as a ghost to scare the counterfeiters. Covered in phosphorescent white paint and fitted with a power pack, Joe 'floats' into the crypt.

Ben Shazar, the Regent of Ardafi, has designs on the throne of the Middle Eastern country. First he arranged the car crash that killed the Sultan. Then he kidnaps the young heir who is attending school in England and must be crowned as per tradition within 24 hours. To save the tiny country from Shazar, win assigns Joe the task of impersonating the young Sultan while the organisation mounts a search. To fool Shazar, they must count on the brain patterns of the Prince's tutor to help Joe pass all the tests. When the villain finds he can't fault the young agent's cover, he drugs his food and arranges a second kidnapping. Shazar's plans continue to go awry when win locates the real Prince and gets him to the coronation. What of Joe — can he be rescued?

The McClaines' efforts to take a vacation are hampered by Sam Loover's appeals that they help on a new mission. Apparently accepting defeat, Sam offers to help them plan their trip and suggests the country of Borova as an ideal spot. Mac and Joe soon discover that Sam has tricked them into going exactly where he wants them. It seems the government has ordered the World Army to quit the Beneleta Base but the Borovans have not dismantled the base as per their agreement. For the sake of world peace, Joe must destroy the facility. Colonel Henderson is the only man with the knowledge and experience of the base's advanced warning system but an injury prevents him from participating in the mission. Joe is given his brain pattern and he embarks on a hazardous assault.

The destruction of a supply rocket spells disaster for two astronauts in an orbiting space station who are dangerously low on oxygen. Since the station forms the hub of win's orbital radar system, the organisation takes command of the rescue effort. Another vital factor is the injury of the astronaut assigned to pilot the supply ship which, therefore, spells another mission for Joe 90. As another rocket is being prepared, Joe gets the pilot's brain patterns which will help him perform the dangerous and difficult docking operation. With two hours of air left, Joe is launched into space. To make matters worse, he finds on arrival that the men have collapsed due to oxygen starvation and Joe must make the docking effort without their help. He succeeds in delivering the oxygen, saving the astronauts but his navigation aerial is damaged in the docking effort. Without it, Joe's capsule falls off course and contact is lost with Earth. The boy must call on all his superhuman skills to re-enter the atmosphere without burning up.

Professor McClaine falls in love with a beautiful American reporter who finds him attractive and shares his interest in electronics. Sam is worried about their many meetings and he finds a willing ally in Joe who views his father's friendship with Angela Davies with growing mistrust. Repeated guestions to Mac draw a blank. He insists that his personal life is no concern of Sam's. Taking a daring gamble, Joe accepts Angela's brain pattern. Under Sam's questioning, it's as if Joe can read her mind and they discover that she is, in fact, an enemy agent assigned to steal the plans of big rat. It is Joe who sees a way to outwit the scheming Angela.

Three win couriers are found shot and their despatch cases stolen. The agency fears that they may have a traitor in their company, a situation that now becomes desperate when win must change all codes and cypher tapes for their eastern network. Harry Sloane, head of the Courier Department, announces that he will undertake the mission himself but Shane Weston will have none of it. Instead, Sloane's brain pattern is transferred to Joe who sets off on the assignment. At first, Joe's movements are puzzling. After arriving in Paris, he suddenly changes aeroplanes and heads for Copenhagen, where he gives win agents the slip. Soon it becomes alarmingly clear that Harry Sloane is really the double agent and Joe is merely following the route Sloane himself had planned. Joe is now in more danger from his own people when Copenhagen receives orders to shoot him on sight! Mac and Sam have a nightmare chase trying to track the boy down. Unfortunately, Harry Sloane finds Joe first and the traitor is determined to retrieve the case at all costs.

World peace hangs in the balance when a heavily armed world Air Force bomber goes off course and crashes in the Arctic near an Eastern Alliance base. The crew ejected safely and all but one of the jet's bombs have been recovered. Unfortunately, the rogue bomb had crashed through the ice and is resting on the ocean floor somewhere within Eastern Alliance borders. win tracks down the one man with the knowledge and ability to recover the bomb, Dr William Kelvin. However, at 70, he is too old to undertake such an assignment and his brain patterns are recorded for Joe. Making their way aboard an icebreaker, Joe is sent out in a tiny one-man submarine but, in his search, he alerts the enemy base to his presence. Just as Joe begins the delicate task of pulling the bomb out of the rock-bed, the enemy killer-subs move in!

Two win agents, Laramie and Fleming, working in Santa Marina, a section of a Far Eastern jungle, are ambushed by enemy agents after receiving a secret report on microfilm. The situation is disastrous as the report contains the covers of every win Agent in the area. Headquarters receives a message from Fleming who has hidden the microfilm but is caught after a chase through the jungle and cannot relay the location of the report. The agent has been imprisoned in an invincible fortress and his partner, Laramie, now lies in a coma. win relies on a library tape of Laramie's brain patterns to aid Joe in the dangerous trek through the jungle. Making his way into the fortress, Joe discovers Fleming has been subjected to a vicious cross examination. Joe struggles to convince the half-conscious agent of his authenticity and find a way to escape. Ducking shots from the enemy, the duo flee into the jungle, trying to evade their recapture and recover the microfilm before it falls into enemy hands.

An international espionage ring is anxious to discover the secrets in a closely-guarded file marked 'File 90'. They also hear about The big rat and kidnap Professor McClaine, pumping him for every bit of information they can. However, they refuse to believe Mac when he tells them the truth about big rat and Joe's secret missions for win. On holiday, in the Alps, Shane and Sam learn that Mac is being held prisoner in a remote Alpine clinic, inaccessible except for a ski lift under clinic control. Joe uses a silent method of rescue, a hot air balloon, but the going is slow and Mac is soon to be tortured!

When sabotage threatens efforts to transport a new and very delicate liquid explosive across Africa to a huge construction site, win are called in to investigate. Joe is given the brain patterns of an explosives expert and a top army driver. He is sent to Africa in the guise of 'Colonel' McClaine with two specially selected Army men at his command. They are astonished when a nine year-old boy arrives but Joe soon gains their loyalty. When the Sergeant is killed in an accident, Joe and Private Johnson press on, climbing into the mountains. Suddenly they receive a message that the Lieutenant at the base is, in fact, the saboteur and he has rigged the explosive containers to detonate at 5,000 feet... and they are just about that height!

Joe fantasises that he is the Sheriff of a town in the wild west of yesteryear. Trouble brews when the win gang ride into town and begin busting up the saloon. They are captured by Joe and thrown into jail. With the bad guys behind bars, Joe leaves the gang in the care of Doc while he goes off on another assignment. However, Doc is overpowered and tied up. To leave no loose ends, the win gang sets the jail on fire but Doc manages to telephone Joe who comes to the rescue. The chase is on and Joe discovers that the gang is planning to rob the Noon express. Melodramatic fighting climaxes in the dramatic rescue of Joe's father who has somehow become involved in the dream.

When General Tempest of Military Intelligence insists that his more efficient organisation should make win obsolete, Shane Weston accepts his challenge to prove who is better. The contest is to be a race with two vehicles and Monte Carlo as the goal. The military is using their high-speed amphibious U-87, while the win team is to rely on Mac's jet-car. Since the race is no-holds-barred, win has Joe accept the brain patterns of a Monte Carlo Rally winner. General Tempest will stop at nothing, from altering signposts to using a jet transporter but the teams reach a road block together. Now it's a straight forward ground race around winding Alpine roads over breath-taking drops. Who'll win?

Aid money sent to a small country to build schools and hospitals becomes the war chest of a dictator who plans to use the ten million dollars to buy arms. The aid was sent in the form of gold bullion and is sealed in the vault of an impregnable castle. When win is sent an appeal for help in the recovery of the gold, Joe is sent into action. Given the brain pattern of the only man in England capable of breaking into the castle, Joe is taken across the border by Mac. The castle is guarded by deadly radio-controlled guard vehicles called Spiders which keep constant patrol but Joe manages to elude them. Using his new skills, Joe cuts his way into the vault with a proton lance. He destroys the alarms as he goes but further danger awaits him as he tries to get the gold to safety.

When test pilot Jim Grant crashes the newest hypersonic fighter plane, win is called in to find out what happened to the aircraft. Grant, who broke his ankle in the accident, is the only person familiar with the plane so his brain pattern is transferred to Joe. Just like the first plane, no faults are located in Joe's so the demonstration for the military brass begins. Joe gives a faultless performance until it is discovered that he can't land the jet! It seems that a mental block about landing had developed in Grant's mind which now threatens Joe's life!

Two convicts escape from a work party in the Canadian mountains. They seize upon the visit of the Prime Minister as an opportunity to get rich quick. A salute is to be fired in his honour from an old gun on a hill overlooking a high railway bridge. The convicts overcome the gun crew and, as the train carrying the Prime Minister crosses the bridge, they blow up each end, trapping the train at the centre. The villains contact the authorities and demand a million dollars ransom and a helijet to make good their escape. Unless their terms are met they promise to blow up the train. Joe and Mac are in Canada on holiday and Joe has the brain pattern of an Olympic bob sleigh champion to help him enjoy himself. They are persuaded by the authorities to take the money and helijet to the convicts. However, Joe is double-crossed and taken hostage. The Prime Minister is rescued before the bridge collapses but Joe is still in dire peril.

Four world statesmen are paralysed after being shot by poisoned darts from a blowpipe. Tests reveal that the poison was developed by the ancient Amaztecs, a civilisation which flourished in the foothills of the Andes. Joe is given the brain pattern of an Amaztec expert and sent to find the antidote. Alone in the jungle, he is captured and brought to the Amaztec temple where he meets their 'God'. The natives have been brought under domination of a white man who has taken power through electronic trickery. Fearful that Joe will expose him as a fraud, the 'God' orders his people to sacrifice the boy but the natives believe that he may be the legendary 'Child of the Sun God'. Now Joe must face trial by entombment to prove that he is a God. He is taken to a cave which is blocked by a stone over the entrance. Joe's only hope of survival is the knowledge he has gained in the brain pattern transfer.

Someone is determined to destroy the world's first hoverliner. A warning that a bomb is placed on board is telephoned to Sir George Harris, chairman of the company that built the liner. The bomb is found but a second threat is received that the liner will be destroyed on its maiden voyage. This time, however, win are involved and the second threat seems a hoax when no bomb is found during a thorough search. Sam, meanwhile, continues to check on the voice pattern of the caller and discovers that it belongs to a man named Johnson Webb. It seems that the man has a grudge against Sir George and his company. Sam visits Webb and secretly takes his brain pattern, before turning him in to the police. Joe is given the saboteur's brain pattern. Now the boy is the only other person who can find the bomb which has been secretly hidden about the hoverliner. Joe finds time against him as he tries to disarm the intricate triple detonator mechanism.

Juan Cordova is the perfect ruler of his small country. He loves his people and will do anything for them. However, his liberal ideas have made him many enemies and his wife fears for his life. She tells win that her husband's pride won't allow any kind of bodyguard, so any protection must be kept secret. Joe is given the assignment on the assumption that Cordova would never suspect him as a professional bodyguard. The president's wife is appalled at the idea of a nine-year-old boy protecting her husband but Joe's knowledge from his latest brain pattern transfer reassures her of his competence. Cordova is blissfully unaware that he is being protected as they travel to a mountain resort. In fact, Joe finds his work cut out for him with bandits at every turn. However, the enemy plots a dangerous final play under water. Can Joe overcome them?

Somewhere in Asia, a win agent observes a vast secret underground rocket complex. Spotted by the enemy, he attempts to get a message back to headquarters. Just as he reaches a border outpost, he is shot in the back but a pen recorder is found on the body which gives Sam and Shane the shock of their lives. It appears that the enemy plans to put a nuclear device in orbit. With that done they can hold the world to ransom. Shane calls in Joe with the mission to destroy the base prior to the launch of the rocket. He will fly the Air Force's most heavily armed fighter, the VG-104. His code name will be Tiger and he will be aided by the brain pattern of an expert on the Eastern Alliance. Refuelling en route, Joe flies in below the enemy radar but he has been spotted. Battling heavy anti-aircraft fire, Joe makes a desperate dive on the complex.

win discovers that the enemy have developed virus X-41 which is capable of breaking down the molecular structure of a building. It will go on destroying everything in its path unless stopped by an antibody. In order to restore the balance of power Joe is dropped by parachute near the enemy research station to retrieve the antibody. With a plan developed with Agent 84, Joe allows himself to be captured by the enemy. The General in charge is amused by Joe's insistence that he is an enemy agent but while the area is being searched for his non-existent accomplices, Agent 84 creates a diversion which allows Joe to steal the antibody. Now he must make good his escape with the information.

Mac, Joe and Brad Johnson, project controller of the Orbital Glide Transport test flight, watch as disaster strikes. The OGT crashes on to the control building, trapping the personnel within. This is the latest in a series of sabotage attempts. Unknown to everyone, Johnson has fitted a special monitoring computer in control to locate the saboteur. The trapped men all manage to escape from control except one: Slade who is really the man responsible for the disaster. He remains in the doomed building to find and destroy the computer before its records can incriminate him. With the brain pattern of a computer and explosive expert, Joe goes down a small bore hole. win has assumed Slade is dead. As the OGT sways precariously above, Joe finds himself face to face with Slade who is armed with a gun.

When Harris, the owner of a small engineering business that has done valuable work for win, has fallen into the clutches of Clayton, a financial shark, the agency decides it's time to teach the man a lesson. Clayton, it seems, will use any method to take control of rival companies while managing to stay just inside the law. Mac goes to his office and pretends to slip a drug into Clayton's tea that will produce hallucinations. win proceeds to convince Clayton that he is seeing things by giving Joe various brain patterns that enable him to do things that no nine year-old could ever do.

His ninth year has been a remarkable one but turning ten seems to depress Joe. It's his birthday and no-one seems to remember the fact. Mac goes out for the day and Mrs. Harris simply apologises for forgetting to send a card. In fact it's all a plot to surprise Joe later that same evening. Sam and Shane join the party and Joe is presented with a huge birthday cake. Over tea, they reminisce about all that has happened to Joe over the year as win's Most Special Agent.