GURPS Infinite Worlds

The shuttles of Infinity Unlimited jump between parallel Earths, seeking adventure, profit, knowledge, and even entertainment. But a parallel called Centrum has also developed the technology to hop between the worlds . . . and they want to rule them all. The Infinity Patrol must deal with their ruthless rivals, as well as with world-jumping criminals, and with the possibility that the secret of dimension travel might escape to some of the really nasty alternate worlds like Reich-5.