Protection | Preview (ITV1)

As much of a conspiracy thriller as it is a police drama, this is the story of a compromised but ultimately honest police officer who is out of her depth yet acutely driven to understand the truth of her lover and how far a case of corruption goes.

Police officer DI Liz Nyles (Siobhan Finneran, Happy Valley, Downton Abbey, Time) works in the secretive and high-stakes world of Witness Protection - when we meet her, she’s juggling a challenging front-line job (with life-and-death consequences for her witnesses) alongside a demanding family life attending to the needs of a teenage daughter, a difficult ex, and a dad recovering from a stroke.

Liz is principled, in control, and scrupulous about the security of her witnesses, particularly the high-risk criminal-turned-informant Jimmy McLennan (Kris Hitchen, The Long Shadow, Four Lives, Trigger Point) and his family. Jimmy is about to testify against his old boss Eddie Crowther (Alec Newman, Karen Pirie, The Last Kingdom), the head of a major organised crime group which has so far evaded prosecution.

As with all those under her protection, Liz goes above and beyond to keep Jimmy’s family safe, working with colleague DS Raj Kohli (Chaneil Kular, Sex Education, Bodies) to keep their whereabouts strictly hidden.

Both at work and at home, Liz has always put others first driven by a great sense of duty as a police officer, mother, and as a daughter - however, recently she has decided to take something for herself and has launched thrillingly – and unwisely – into a secret affair with a married and more junior colleague in DS Paul Brandice (Barry Ward, Bad Sisters, The Capture).

One morning, a devastating incident at work raises grave questions about the integrity of Liz’s unit, which is rocked with accusations of corruption: it is believed that someone has been leaking information to organised crime. Liz begins to wonder with horror if she has unwittingly compromised herself, if indeed her secret lover Brandice has sinister motives and has been using her.

While a police team led by the formidable DCI Hannah Wheatley (Katherine Kelly, Mr Bates vs The Post Office, Criminal, The Long Shadow) investigates the incident, Liz secretly launches her own unofficial investigation. In this she must avoid the watchful eye both of Wheatley and of the inscrutable DCI Amanda Kelma (Nadine Marshall, Champion, Sherwood, Trigger Point) from Professional Standards, who has been tasked with weeding out corruption in Liz’s unit.

It’s a tense and febrile atmosphere within the force as Liz pursues her off-the-books investigation and brings her into further conflict with the very police officers investigating her. As Liz starts to uncover the truth, she is confronted with disturbing and dark possibilities, raising questions not only about Brandice but also her team and her colleagues in the wider police force.

Chasing clues to which she shouldn’t strictly have access, Liz finds herself transgressing in ways she wouldn’t previously have dreamt of and bringing danger ever closer to her door. As the series progresses, single mum Liz becomes increasingly torn between her dedication to her family, her loyalty to her lover, and her duty towards her witnesses.

In struggling to unravel the mystery, she is drawn into a complex and clandestine world, coming up against various opaque, secret organisations operating at cross-purposes, and in rivalry to one another.

Protection begins Sunday 16th March at 9pm on ITV1.