It has been a complex and sometimes confusing watch, but now the time-shifting thriller really delivers with a powerful and unbelievably tense swansong.

Following the revelation that DI Elaine Shepard is the real acid killer, her dark motivation is explored and the truth about her disturbing past is finally revealed.

As Gabriel’s own challenging history is also brought to light, along with another shocking secret, a dangerous cat-and-mouse game begins between the lovers and colleagues.