Tinker, Spacer, Psion, Spy details over eighteen careers specifically for use in the Twilight Sector Campaign Setting, but is easily adaptable for Mongoose Publishing's Traveller setting. More than just a careers book, thic companion also includes details on the latest in cyberware out of the Oster Republic called CyrgeWare, plus information on powered armor and Twilight-variant Psionics, Extended Basic Training Skill Packages, rules and tips for Longevity and Alternate Injury Tables, plus charts for creating worlds specific to The Twilight Sector.