Thandie Newton | BBC

Line of Duty is notoriously ruthless when it comes to killing off key characters in this amazing cop thriller.

In series three, Sergeant Danny Waldron – played by Daniel Mays – died in the very first episode, and Jason Watkins’s Tim Ifield didn’t fare much better in the current series, being found dead and relieved of several fingers in episode two.

Now this episode tonight took a dark dark twist.

DS Arnott continued to investigate Roz Huntley by going after her husband to get a statement of her whereabouts. When he goes to visit him at the end the “balaclava man” ends up being there and attacks Arnott seemingly killing him. Could it be Roz’s husband all along?

It seems he got changed a little quick leaving viewers shocked and even more confused

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