The "Line of Duty" cast have been warned they face "serious penalties" if they give away any of the show's secrets.
The BBC police corruption drama's latest series draws to a close on Sunday (30.04.17) evening, and with fans on the edge of their seats to discover the identity of "Balaclava Man", those working on the show have been warned to stay tight lipped until the credits role.
A source told The Sun on Sunday newspaper: "The cast's contracts stipulate they can't give away the show's secrets.
"That is the last thing any would want to do but if they did by accident they would be in breach of contract.
"And the consequences could be serious. They might even face financial penalties."
While the resolution to the gripping series - which fans will hope will show the fate of DCI Roz Huntley (Thandie Newton), unmask DS Steve Arnott's (Martin Compston) attacker and reveal the identity of the mysterious, corrupt, high-ranking officer "H" - is being kept tightly under wraps, Vicky McLure, who plays DS Kate Fleming, has promised fans won't be disappointed.
Speaking before last week's episode, she teased: "So much happens in the last two hours. It is great."
Vicky's character often goes undercover to find out hidden information as part of her unit's investigations and she recently teased she thinks that will have to change if she's to return for a fifth series.
She said: "You can only be undercover so often, so if I am in series five there will have to be some changes."