They've always been a great team. But now, President Frank Underwood and his wife Claire become even greater adversaries as their marriage stumbles and their ambitions are at odds.

The grisly aftermath of the latest attack reveals a foil to the killer's plan. Frantic and infuriated, Spector flees the crime scene and hastily disposes of evidence, all while trying to keep his home life from falling apart. Gibson inches nearer to uncovering the perpetrator's identity, but an unexpected turn brings them closer than ever.

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.

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.