Episode 1
A chance encounter means Luther might be on the verge of finding love. But nothing comes easily - not when a fetish killer is on the hunt, not when an internet tormentor has had the tables turned and not when his worst enemies are his own colleagues.
Episode 2
Luther discovers the fetish killer is re-enacting the past. Can he stop him before he kills again? Meanwhile Ripley has to choose whether to turn a blind eye to Luther's unorthodox policing or betray him on record.
Episode 3
Luther must confront his demons when a vigilante killer embarks on a crusade to punish past offenders. Meanwhile the campaign within the force to bring him down knows no bounds, threatening everything Luther holds dear and pushing him to his limits.
Episode 4
Accused of crimes he hasn't committed, Luther must work quickly to clear his name and stop the vigilante killer from becoming a martyr. But in becoming the killer's target, it's not just his own life he risks, but the lives of those he loves.