Macdonald will star as Detective Chief Inspector Joanne Davidson, who draws the attention of anti-corruption unit AC-12 for her unconventional conduct during the investigation of an unsolved murder.
Filming on World Productions’ drama, created by Bodyguard’s Jed Mercurio, will begin next year. Martin Compston, Vicky McClure and Adrian Dunbar will reunite as the AC-12 officers investigating Macdonald’s character.
Mercurio said Davidson will “prove the most enigmatic adversary AC-12 have ever faced.” Macdonald joins Stephen Graham, Keeley Hawes and Lennie James, who have played police officers under investigation in previous series of Line Of Duty.
The series five Line Of Duty finale was the most-watched program of the year so far in the UK, with a 28-day figure of 13.7M viewers across TV and online.