When the investigation into a Belfast architect’s murder goes cold, Detective Superintendent Stella Gibson arrives from London to lend her expertise. At the same time, Paul Spector outwardly a grief counselor and family man, secretly a depraved killer, plans his next attack, on young lawyer Sarah Kay.

When Kay is found dead in her home, Gibson convinces the local police to put her in charge of the investigation, certain the crime betrays the work of a serial killer. Having taken a few keepsakes from his victim, Spector grows enraged when he suspects that his flirtatious babysitter has snooped in his office.

Gibson’s relationship with detective James Olson comes under scrutiny in the wake of his assassination. Meanwhile, she holds a press conference alerting the city of Belfast that the three murders may be linked. On a visit to his in-laws’ house, Spector finds an empty shack and feverishly fantasizes about the victim he’s picked to take there.

As the sordid details and big names attached to Olson’s death come out, the investigation takes a tragic toll. Gibson, however, catches a break: the killer contacts one of his victim’s families. But will she be able to act before another woman falls prey to Spector’s madness?

The killer's latest attack gives Gibson renewed impetus and as the net appears to be closing in, Spector makes a dramatic confession and a decision that binds his fate to Gibson.

Gibson tries to help Spector's surviving victim remember her attacker's identity; Spector deals with the loose ends he left behind.