A woman is found decapitated along a bike path adjacent to Lake Michigan, and Chicago detective Joe Erickson is called in to investigate the grisly crime. A jogger who came upon the body reported seeing a hooded, black-clad figure resembling a ninja sprinting away. As Joe and his partner, Sam Renaldo, investigate, two more people are attacked in the same way, and witnesses once again report seeing a hooded, masked figure hurriedly exiting the scene. Is this the work of some deranged individual acting out a sick fantasy, or what? Joe and Sam attempt to piece together scant evidence before the killer strikes again. But their investigation has proven frustrating, as they have found no real suspects, and the three victims seem to have nothing in common. That is, until they happen upon the one aspect that links all three victims and points them toward the killer.
