DCI Ross Tanner of the Special Murder Unit is working on a case with the ambitious DI Catherine Tully when he makes the frightening discovery that he is slowly losing his sight. Tully discovers his secret and agrees to cover for him, on certain conditions.

DCI Tanner and company try to work through an ever-growing list of suspects for the murder. Tanner suspects that Matthew's stepfather, Adam, is hiding something, but does that make him the killer?