Young security officer Baro Harkless, an idealist driven by the memory of his heroic father, and jaded Luff Imbry, a mountebank, swindler, and forger of the first water, form an uneasy truce when they discover a common goal: capturing the greatest conman of them all, Horselan Gebbling.
Gebbling has chosen as his prey the victims of the first new disease in millennia, the invariably fatal ailment known as the lassitude. He dangles in front of his victims the fabled gemstone called black brillion. About black brillion, learned men agree on only two things: it can do anything, and it doesn't exist. But Gebbling boasts of having it, and its effects on the lassitude are nothing short of magical.
Baro and Luff get caught up in an ever-growing tangle of mysteries. And the dangers are not merely physical. On the ship is a noönaut, and explorer of the Commons, the dream realm which contains the memories and emotions of hundreds of thousands of years of human existence. And something in the Commons is calling to Baro to claim him for its own.
