In Old Korvosa, nightmare-spawned horrors begin stalking the district's shiver addicts, sparking a manhunt to bring those responsible to justice. What role does the strange cult known as the Brotherhood of the Spider play in the mysterious deaths, and why is the veil between the dreaming and waking worlds so thin? To solve these mysteries and others, the heroes must walk the unseen paths of Bridgefront's occult underworld, and even enter the Dimension of Dreams itself to unravel the web of intrigue concealing the cult's deadly machinations. But what will happen when the heroes' own dreams turn against them, and what becomes of those who uncover esoteric secrets too terrible to know? Beset by dangers from their own minds, the heroes must race against time to save Korvosa—and their sanity.