Also returning for the four-part installment are Dermot Crowley, Michael Smiley and Patrick Malahide.
Wunmi Mosaku joined the ensemble as Police Detective Sergeant Catherine Halliday.
"It's good to be back in London, back in the coat," Elba said in a statement Thursday.
"We missed John Luther. We missed some old friends. And we wanted to make the biggest, scariest, darkest, most thrilling series of Luther there's ever been. So, that's what we've come back to do," series creator Neil Cross added.
"When the moonless shadows of London give birth to a new nightmare, [Detective Chief Inspector] John Luther must once again confront the depths of human depravity," a network synopsis said.
"As a series of monstrous killings becomes ever more audacious, Luther and new recruit D.S. Catherine Halliday are confounded by a tangle of leads and misdirection that seems designed to protect an unspeakable horror."
"But, even as the case brings him closer than ever to the nature of true evil, a reluctant Luther must also face the ghosts of his own past. Striding back into the line of fire, he must choose who to protect... and who to sacrifice."
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"Whatever his next move, it will have devastating consequences for those around him -- and change John Luther forever."
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