When Simon Johnson is attacked in his LA apartment, he knows he must defend himself or die. Turning on the lights after the scuffle, Simon realises he has killed his attacker and the resemblance of the man to himself is uncanny. He embarks on a gripping existential investigation, into his own murky past, and that of Jeremy Shackleford, the (apparently) happily married math teacher whose body is now lying in Simon's bathtub under forty gallons of ice.