Venice, 1888. A killer haunts the calles and canals of the Floating City, a killer that many claim is 'Il Sonnambulo' - the Sleepwalker - a mythical figure familiar from old tales and nursery rhymes.Art student Vittorio Innocenti is convinced he has identified the murderer, but only Commissario Voza, the 'magistrates lackey', believes the young man and fully understands the danger. Soon, Il Sonnambulo will prove how untouchable he is, and how deep his depravity goes.