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A veteran beat cop and teenage girl fall to their deaths from a tower block in south-east London, leaving a five-year-old boy and rookie police officer Lizzie Griffiths on the roof, only for them to go missing. Detective Sergeant Sarah Collins is drafted in to investigate, working to find Lizzie before she comes to serious harm, but also to uncover the truth behind the grisly tower block deaths.
DS Sarah Collins is called to the brutal stabbing of a teenager, but her investigation soon finds itself at cross purposes with a covert operation led by Kieran Shaw, who is working with Sarah's old partner Steve Bradshaw, now deep undercover. Meanwhile, Lizzie Adama is back at Farlow trying to balance her new role as a detective with family life, but her path and Kieran's are about to cross.
Sarah and Elaine uncover a disturbing link between their ongoing investigation and a brutal hit-and-run. Kieran urges Lizzie not to reveal the secrets of Operation Perseus.
Kieran and Baillie share some information that could help Sarah make an arrest but her reluctance to cooperate leaves them exasperated. Shakiel puts Steve's loyalty to the test.
Operation Perseus reaches its climax as Kieran prepares to catch Shakiel with a car-load of automatic weapons. However, Spencer's killer, Jermaine King, has escaped from custody and kidnapped Ryan's sister, Tia.
Gemma Whelan
DI Sarah Collins
Tahirah Sharif
DC Lizzie Adama
Jimmy Akingbola
DC Steve Bradshaw
Emmett J. Scanlan
DI Kieran Shaw
Bobby Lockwood
DC Lee Coutts
Ella Smith
DS Elaine Lucas
Karl Davies
DCS Tim Bailie
Michael Karim
PC Arif Johar
Daniel Adegboyega
Shakiel Oliver
Laurie Delaney
Mary Shaw
Lamar Waves
Ryan Kennedy
Robbie Gee
DS Mark Angel
