The show stars Holywood's Jamie Dornan as serial killer Spector and X-Files FBI agent Gillian Anderson as tough-talking detective Gibson.
Gibson, seconded to Belfast from the Metropolitan Police, is tasked to sniff out serial killer Spector who stalks the city streets for his female prey.
It had been touch and go at the end of series two in an excruciating cliff-hanger as Spector lay shot in the arms of detective Stella Gibson.
But now, with Spector very much alive, viewers on Thursday night were given a miserable insight into what perhaps turned him into the killer that has graced our screens for three series.
The penultimate episode gave a harrowing look at the life of a young Spector, which detailed the suicide of his mother when he was 8-years-old and the subsequent abuse he suffered in a care home.
It was difficult viewing as the audience listened in on Spector's conversation with the psychologist.
We learned how Spector grew up being jealous of the happy lives of others and in an unexpected twist Spector was implicated in to the killing of a woman in London in 2002, a time before his supposed amnesia.
Speaking previously about series three, Dornan said: "You can expect the unexpected. There's quite remarkable turns in the third season that I really genuinely think people won't see coming that are hugely exciting."
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