Line of Duty: BBC Two, 9pm
The gripping drama comes to an end tonight, and the team makes an important discovery.
Detective Lindsay Denton's motives are still being questioned - some are convinced of her innocence, while others remain wary of her. Kate is adamant that Lindsay was involved in the ambush, and worries about Steve's trust in her.
Meanwhile, the identity of 'Caddy' is still plaguing the team.
Law & Order: UK: ITV, 9pm
After a psychiatrist is found stabbed to death, Ronnie and Joe believe one of his violent patients is the culprit. However, as the investigation continues, they discover details from his personal life that cast suspicion on his wife Alison.
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As the case builds around Alison and she is taken to trial she begins to lose her composure, leaving the team torn. Jake is determined to see justice done, while Kate questions whether the case is valid at all.
W1A: BBC Two, 10pm
W1A, the follow-up to London Olympics mockumentary Twenty Twelve, launches tonight.
Hugh Bonneville returns as Ian Fletcher, who is tasked with moving the BBC further into the digital age as the corporation's new head of values.
Ian has to deal with a challenging team including Anna Rampton, who always believes she is right, and Will Humphries, who's still not exactly sure what he is doing or how he wound up there in the first place.
Castle: Channel 5, 10pm
Castle returns from its mid-season hiatus tonight. A retired, terminally ill detective gets into contact with Beckett, claiming that he now wants to come forward with information regarding Beckett's mother's murder 12 years ago.
However, before Beckett can hear the revelation the older detective is suspiciously murdered, leaving vital clues unattainable. As Beckett continues searching for the truth, her emotional stability is called into question.
