Line Of Duty - the police corruption drama that has had more than eight million viewers on the edge of their seats - reaches its series finale tonight.
The fourth series of the BBC1 drama, starring Thandie Newton as DCI Roz Huntley, has been a huge hit with viewers.
A fifth series of the show, which casts a new star for each season, has already been commissioned.
Viewers hope to find out who the so-called Balaclava Man is during the final episode.
Actor Patrick Baladi, who plays lawyer Jimmy Lakewell, recently said everyone is a suspect.
He told Good Morning Britain: "What's interesting is Roz Huntley's character, and how she's going to redeem herself, if that's possible - if she's not the culprit, the light of suspicion is shone on everyone.
"Even, I would say, (Supt Ted) Hastings (Adrian Dunbar) - who hasn't been considered as a suspect."
The fourth series has seen its number of viewers grow steadily since the show moved to BBC1 this year, with 8.5 million viewers.
The previous three series aired on BBC2, where audiences peaked at 5.6 million.
:: Line Of Duty airs at 9pm on BBC1.