Sam Loover, a friend of Mac and an agent of the World Intelligence Network (WIN), recognises the potential of Joe and the BIG RAT and persuades Mac to pledge their services to the organisation. With the aid of the BIG RAT, Joe becomes a spy unlike any other: by taking on the brain patterns of expert adults, he gains the skills needed to undertake dangerous missions, while his youth helps him to avoid arousing enemy suspicion. As long as he wears a pair of special glasses, which contain electrodes that store the transferred brain patterns, he is able to carry out all manner of assignments – from piloting fighter aircraft to performing neurosurgery to playing the piano. Known as WIN's "Most Special Agent", Joe 90 reports to Shane Weston, the network's commander-in-chief in London, and carries a specially-adapted school case that contains radio transceiver and high-capacity handgun. The series ends with a clip show episode set on Joe's 10th birthday, in which a number of his missions are recalled as flashbacks during a surprise party.