The Nightwalker

German author Fitzek makes his U.S. debut with a lurid thriller. After Leon Nader lost his parents in an accident at age 10, he suffered bouts of sleepwalking, requiring treatment with sleep specialist Dr. Samuel Volwarth. As an adult, Leon again turns to Dr. Volwarth after his wife, Natalie, flees his house in an unnamed city in terror, with a bloodied mouth and a black eye Leon fears he inflicted while sleepwalking. Provided with a camera to track his night movements, Leon begins to suspect his waking hours disguise a sinister second life—buried in the vaults and crawlways of his apartment complex, built by the mysterious Albert von Boyten—or maybe just the inner channels of his tormented mind. As Leon’s nightly searches intensify, Fitzek vigorously whips the plot into a frenzy of hypnagogic secrets, sex, and sadism. The protagonist’s paper-thin characterization undermines the emotional stakes of Leon’s desperation, and after a stretch of serviceable suspense, the book’s final twist strains plausibility, landing with an expository thud. (Feb.)