Pentonville Prison, 1917. Wally Hubbard is serving a long sentence for arson, but makes an audacious escape after befriending and tricking one of his guards. Death threats were made against Inspector Marmion, who arrested him, and he is warned to watch his back. However it soon becomes clear that Hubbard has eyes for only one man: Ben Croft, the man he holds responsible for the death of his daughter. The search for Hubbard is soon tangled with a murder investigation, mired in confusion, as the identities of killer and victim become increasingly ambiguous. With mounting pressure from his superintendent to recapture Hubbard and unravel the mystery surrounding the murder, along with concern for his withdrawn son, Paul, and the involvement of Special Branch only complicating matters further, Marmion tries desperately to untangle all the threads . . .