I'm a big fan of alternate histories. The two GURPS Alternate Earths books published a few years back for the old 3rd Edition of GURPS are among my all-time favourite RPG sourcebooks. Still, it rather surprised me when I first heard that Steve Jackson Games had chosen to make this meta-setting the core background for the fourth edition of GURPS 4th Edition of the Generic Universal Roleplaying System. Although the previous AH books were superb pieces of work, Alternative History and Time Travel games have never been hugely successful commercially.

Genius conspiracy theory expert Ken Hite took on the task of taking the existing hard-SF Alt-History of Alternate Earths and adding some of his trademark 'high weirdness'. Hints over the internet in the preceding months promised the addition of sinister occult conspiracies and terrifying extradimensional Things Mad Was Not Meant To Know (think Lovecraft minus the seafood) and just about everything else. This would give us a game setting which encompasses swashbuckling adventure, hard science fiction, high fantasy or dark horror, or all of these at once.

In the hands of a lesser author, there's a grave danger than it would turn into a cheesy Abbott and Costello style monster mash. But has Infinite Worlds managed to avoid that fate?

Chapter One, Infinity Unlimited describes the world called Homeline, a world not unlike our own, but a world where a physicist named Paul van Zandt discovered the means of travelling between worlds, and ultimately founded the Infinity Unlimited, a corporation chartered by the United Nations to explore these alternative worlds.

The bulk of the chapter is given over to the Infinity Patrol, a likely employer of player characters. They're described as a supranational paramilitary agency, under Infinity's control, dedicated to protecting Homeline, 'The Secret', Infinity itself, and the unknowing innocents of other worlds, in roughly that order. 'The Secret' is the knowledge of parachronic travel, which must never be revealed to the inhabitants of other timelines! The chapter describes the mission and goals of the Infinity Patrol, their structure, technologies, and something of the physics of dimensional travel. As well as the Patrol, there are other timeline-hopping outfits licenced by Infinity, from the interdimensional White Star Trading, who actually provide Infinity with much of their revenue, Time Tours, who send parties of tourists to relatively 'safe' timelines, and the interworld mercenary company Alternative Outcomes.

Chapter Two, Enemies Everywhen describes the principal villains of the setting. It starts with two parallel worldlines that have discovered the secret of parachronic travel.

First is the technocratic and vaguely communistic Centrum, seemingly intent on taking over every parallel world they can get hold of. Their parachronic technology works on similar principles to those of Infinity, albeit with subtle differences. Centrum are not completely evil, but they are totally ruthless and believe the end justifies the means. They tend to operate in the shadows, taking over existing power structures from within rather than using brute force. For a shades-of-grey cloak-and-dagger style of game, they make a worthy adversary for the Infinity Patrol. It's even possible to make Centrum the good guys, with a darker version of Homeline becoming the villains.