The Colour of Magic recap

Rincewind, an incompetent and cowardly wizard of Ankh-Morpork, is ordered to protect Twoflower, the Discworld's first tourist, a naive and wealthy insurance clerk from the far Agatean Empire who travels with a fortune in gold and a homicidal walking chest called the Luggage. Their misadventures begin when Twoflower's talk of insurance burns Ankh-Morpork to the ground, and they flee the city with Death and other dangers close behind. They pass through a temple of the ancient evil Bel-Shamharoth, the Sender of Eight; visit the Wyrmberg, an inverted mountain of imaginary dragons ruled by the dragonrider Liessa; and are finally carried to the very Rim of the flat world, where the kingdom of Krull means to launch a ship over the edge and sacrifice them. Escaping, the two are instead swept over the Rimfall. The book ends with Rincewind and Twoflower plunging off the edge of the Disc into open space, their story left hanging.

In Ankh-Morpork the failed wizard Rincewind meets Twoflower, the Disc's first tourist, a cheerful insurance clerk from the distant Agatean Empire who has come to see the world and carries a fortune in gold and a walking chest, the Luggage. The Patrician orders Rincewind to guard the visitor and keep him alive. Twoflower's foreign notion of insurance quickly catches on, and when a tavern owner sets fire to his own premises to collect on it, the blaze spreads and consumes much of the city. Rincewind, who had meant to rob Twoflower and slip away, instead ends up fleeing the burning city at his side, pursued by trouble and by Death himself, who keeps arriving to collect the wizard only to be foiled.

Away from the city, Rincewind and Twoflower travel into wild country, unaware that their fates are literally being gambled over by the gods at a gaming table. They fall in with Hrun the Barbarian, a famous hero, and are drawn to a dark temple dedicated to Bel-Shamharoth, the Sender of Eight, an ancient evil tied to the forbidden number. Trapped inside, they barely survive an encounter with the creature and escape the temple.

The companions come to the Wyrmberg, an upside-down mountain ruled by dragonriders who conjure dragons out of their own imaginations. Twoflower, whose mind is vivid enough to summon a dragon of his own, is caught up in a struggle for control of the mountain between Liessa Wyrmbidder and her brothers, and Hrun becomes entangled in Liessa's schemes. Rincewind and Twoflower escape when their imagined dragons carry them off the mountain, and they fall clear of the Wyrmberg toward the Rim of the world.

The pair are carried to the very edge of the Disc, where the endless waterfall of the Rimfall pours off into space. They reach Krull, a kingdom perched at the Rim whose scholars intend to launch a great bronze vessel over the edge to learn the sex of the Great A'Tuin, and who plan to sacrifice the two travellers to the project. Rincewind and Twoflower escape, but in doing so are swept over the Rim. The book ends with them going over the edge of the world and falling into the void, their fate unresolved.

The Colour of Magic ends on a literal cliffhanger. Having escaped the scholars of Krull at the Rim of the world, Rincewind and Twoflower are swept over the edge of the Disc and fall, together with the Luggage, off the Rimfall waterfall and out into the void beyond the world. Nothing about their fate is resolved: they simply go over the edge and keep falling, with no rescue and no landing. The two remain bound together, the reluctant wizard and the relentlessly optimistic tourist, still pursued by the bad luck that has followed them the whole way. The larger questions of the setting are left open as well, chief among them the riddle the scholars of Krull hoped to answer, namely where the Great A'Tuin, the star turtle carrying the Disc, is swimming to and why. The story continues directly in the next book.