When a man is murdered while working as a pizza delivery driver in London, DI Kip Glaspie (Carey Mulligan) arrives on the scene – but what she finds opens up more questions than it answers.
This four-part drama by screenwriter Sir David Hare, produced by BBC2 and Netflix, is directed by SJ Clarkson and goes beyond your usual TV thriller to become a state-of-the-nation drama encompassing politicians, vicars, and asylum seekers.
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Here are the characters you'll meet – and where you've seen the actors before...
Carey Mulligan – DI Kip Glaspie
Who does Carey Mulligan play? Kip Glaspie is an ambitious and talented detective inspector who leaps at the chance to take on a murder case. She is very good under pressure and likes a challenge. Kip is pregnant, but it's irrelevant to her job and to the show; she is emotional, but never overwhelmed.
Where have I seen her before? After roles in Bleak House, Pride & Prejudice (as Kitty Bennet) and The Amazing Mrs Pritchard, Carey Mulligan became a household name when she starred in An Education – a performance which earned her a Best Actress nomination at the Oscars. Over the last decade, memorable roles include Daisy Buchanan in The Great Gatsby, Maud Watts in Suffragette, and Jean in Inside Llewyn Davis. The actress also played Sally Sparrow in iconic Doctor Who episode Blink.
Billie Piper – Karen Mars
Who does she play? We first meet Karen when she opens the door to the pizza delivery boy with a crying baby on her hip and a daughter in the other room. She's posh and cross, and spends her evening pacing, smoking and drinking.
Where have I seen her before? Billie Piper was the Doctor's companion Rose Tyler in Doctor Who. She has also starred in Secret Diary of a Call Girl, Penny Dreadful, and – on stage – in hit play Yerma.
John Simm – David Mars
Who does he play? David Mars is a Labour MP who is fed up of being in Opposition. He's frustrated with his leader and his devotion to his job has just caused the breakdown of his latest relationship.
Where have I seen him before? Like Billie Piper, John Simm appeared in Doctor Who, playing the Master. He is also famous for his role in time-travelling police drama Life on Mars, with other roles including The Catch, Intruders, The Village, Mad Dog, and Exile. It's clearly John Simm season on TV at the moment because he's also starring in Trauma, airing at exactly the same time over on ITV.
Nicola Walker – Jane Oliver
Who does she play? Jane Oliver is a gay vicar and a self-proclaimed "mess". She is deeply devoted to her girlfriend to the point of clinginess and neediness.
Where have I seen her before? Nicola Walker plays DCI Cassie Stuart in the TV series Unforgotten. She previously played Gillian in Last Tango in Halifax, and Sharon in Babylon.
Hayley Squires – Laurie Stone
Who does she play? Laurie Stone manages a takeaway pizza restaurant in London. She was the one who sent Abdullah to deliver the regular Monday night pizza to Karen Mars (Billie Piper) in place of her other delivery boy Mikey.
Where have I seen her before? Over Christmas we saw Hayley Squires as Cornelia in The Miniaturist. She also recently appeared as a waitress in Philip K Dick's Electric Dreams alongside Timothy Spall, and played Katie in I, Daniel Blake.
Jeany Spark – Sandrine Shaw
Who does she play? That would be a spoiler.
Where have I seen her before? Fans of TV series Man Down will recognise Jeany Spark as Emma. Her other credits include Born to Kill, Jericho, Wallander, The Interceptor, Da Vinci's Demons, and Claire in Line of Duty.