After spending a night with Zoe, Luther believes they are now back together. Meanwhile, serial killer Henry Madsen, the man responsible for Luther's extended leave, has woken up from his coma.
And across London, four young women have been murdered, yet despite hundreds of hours of surveillance footage and the huge pool of witnesses, no connection can be found between them. But the time between murders is decreasing - whoever this killer is, he's going to keep killing until he's caught.