Meet the cast of The Loch

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Producers say the Loch itself is a character in this murder mystery. But we couldn't exactly write a character description for a body of water, so here are all the human characters instead – and where you've seen their faces before:

Laura Fraser – DS Annie Redford

Who does she play? Annie Redford is a dedicated – but dissatisfied – Detective Sergeant in rural Lochanfoy. She has a strained relationship with her teenage daughter Evie, and a loving one with husband Alan. But when the town is hit by a brutal serial killer, she is horrified by what is happening to her community – and also excited about the career opportunity a murder case could present.

Where have I seen her before? Scottish actress Laura Fraser starred as Eve Stone in The Missing. She played Juliet in One of Us and was Lydia Rodarte-Quayle in Breaking Bad.

Siobhan Finneran – DCI Lauren Quigley

Who does she play? Glasgow detective and single-minded career officer Lauren Quigley is brought in to lead the investigation. She's under no illusions about the darker side of human nature, and as an outsider she can see clearly that the killer is probably hiding in plain sight. A no-nonsense policewoman, she wants to catch the culprit and get back to her home city to secure the promotion she has been working towards for her entire career.

Where have I seen her before? Siobhan Finneran recently starred as Clare Cartwright in Happy Valley. She played a very different character, Janice Garvey, in Benidorm – and also took on the role of Mandy in TV series The Syndicate. But many ITV viewers will know her best as lady's maid O'Brien from Downton Abbey, a scheming servant and one-time friend of Thomas Barrow.

John Sessions – CI Frank Smilie

Who does he play? Frank Smilie is a traditional old-school cop nearing the end of his career. He doesn't want any drama and will look after his own – even if that means bending the rules. He has worked with Lauren Quigley before, and the two don't like each other very much. Now Quigley is also a DCI and back in town, it's a case of "two Chiefs, one territory".

Where have I seen him before? John Sessions has recently been on the big screen in Florence Foster Jenkins. On TV he has taken on roles in Upstart Crow, Jonathan Strange & Mr Norrell, Outlander and Mr Holmes.

Gray O'Brien – Alan Redford

Who does he play? Alan Redford is Annie's husband. He works as a local tour boat operator telling tales of the Loch Ness Monster to tourists. He adores his wife, but the murder case drives a wedge between them.

Where have I seen him before? Gray O'Brien had a three-year stint as Tony Gordon in Coronation Street, a role which earned him the Villain of the Year title at the British Soap Awards 2009.

Shona McHugh – Evie Redford

Who does she play? Evie is the only child of Annie and Alan. Aged 18, she's spirited, rebellious and keen to leave school for a new life in Australia. A (pretty weird) teenage prank involving bones from the local abattoir arranged in the shape of Loch Ness monster lands Evie and her friends in trouble when a human heart turns up in this fake "Nessie".

Where have I seen her before? This could be a breakout role for Shona McHugh, who was last on TV in Waterloo Road in 2006.