Idris Elba returned to his iconic role as the titular detective in BBC One crime drama Luther on Tuesday night. The kick-off of the next chapter in the Neil Cross created show averaged 5.6M viewers in the overnights, peaking at 5.9M, and was the most-watched program of New Year’s Day in the UK. A 25.7 share is the highest the series has earned across the debuts of its five seasons while the number of viewers ties with Seasons 1 and 2. Luther will air on BBC America in the U.S., though a date has not yet been announced.

The multi Emmy-nominated series, which is produced by BBC Studios, also stars Dermot Crowley, Michael Smiley and Patrick Malahide. For Season 5, Wunmi Mosaku joins as new recruit DS Catherine Halliday and Hermione Norris is playing Dr Vivien Lake, a psychiatrist who cares for some of the most vulnerable in society. There’s also a key returning character.

In Season 5, DCI John Luther is once more called to immerse himself in the deepest depths of human depravity. While monstrous and seemingly indiscriminate killings become ever more audacious and public, Luther and Halliday are confounded by a complex tangle of leads and misdirection that seems designed to protect an untouchable corruption. But even as the case brings him closer than ever to the true face of evil, a reluctant Luther is forced to confront the unburied demons of his own recent past. Striding back into the line of fire, he must choose who to protect and who to sacrifice. His next move will have devastating consequences for those around him — and change him forever.

Luther’s Season 4 aired as a two-hour TV movie in December 2015, so it’s been a long wait for further installments. Its launch was the series’ lowest with 4.9M overnight viewers. Prior to that, Season 3 debuted in July 2013 with 5M while Seasons 1 and 2 both scored 5.6M.

Elba recently said Season 5 is not the end of Luther, “but there are some real changes that will happen.” He may have been alluding to the feature film that’s been tipped. Cross has previously told Deadline that he was “absolutely” still toying with that idea.

The four-part Season 5 was commissioned by Piers Wenger and Charlotte Moore for BBC One. Executive producers are Elba for Green Door Pictures, Cross, Marcus Wilson and Hilary Salmon for BBC Studios and Elizabeth Kilgarriff for the BBC.