There was a time when the Earth had three moons, and when the seductive sorceress Avalona could alter futures and bend "happentracks" with her spells.

Indeed, in this vast chaotic universe called the Greataway, with its many imaginable futures, anything is possible. Especially when Nyneve, Avalona's bewitching human disciple, conjures up the complete legend of Camelot and when the roguish gnome Fang, slayer of the dread daggertooth, stumbles into the human happentrack, causing human and gnome worlds to overlap.

For then the moons begin to disappear one by one, and Fang, Nyneve, and all their comrades find themselves caught in a happentrack from which there is no escape, a happentrack in which the legend of Arthur might prove their only salvation...