Anna Maxwell Martin will reprise the role of senior anti-corruption Detective Chief Superintendent Patricia Carmichael.
Elsewhere, fans believe DI Steve Arnott (Martin Compston) discovered some key information off-screen that he’s holding back from Hastings in the latest episode.
The latest episode of Jed Mercurio’s series ended with the revelation that DCI Joanne Davidson (Kelly Macdonald) was related to a character from a previous series.
A formerLine of Duty cast member is returning in the next episode.