Line of Duty fans are eagerly awaiting the next instalment - and it's set to get even more complicated for AC-12.
Episode four left viewers of the BBC One cop drama on the edge of their seats on Sunday night and this weekend, a past face is returning.
And it's "not good news for the gaffer," says creator Jed Mercurio.
Anna Maxwell Martin will reprise her role as Detective Chief Superintendent Patricia Carmichael, the BBC has confirmed.
For fans now searching their memory for when she was last around, Carmichael appeared in series five when she was brought in as an independent investigator amid doubts over the integrity of Superintendent Ted Hastings.
Her return comes as Ted, played by Adrian Dunbar, is facing a forced retirement and a new merger between AC-3, AC-9 and AC-12.
But with DI Steve Arnott completely unaware about Ted's latest meeting with DCC Andrea Wise, Carmichael's return is likely to ruffle feathers.
Anna Maxwell Martin has said of her comeback: “Pat’s back, I can’t remember what she’s doing there, nor would I be allowed to blab, but suffice to say she’s got some new clobber and she’s ready to bust some balls."
It also comes as the net closes in on DCI Joanne Davidson with episode four ending in dramatic style as they discovered a DNA match to another person in the police records.
This left viewers taking extreme measures to try and see the file Ted had hold of revealing all the information presented to him by DI Arnott and AC-12's newest recruit DC Chloe Bishop.
Line Of Duty continues Sunday night at 9pm on BBC One and BBC iPlayer.
