A half crime Drama/half legal procedure focusing on the Criminal Investigation Department (C.I.D) Detectives who investigate murders involving the people on the streets of London and the Crown Prosecutors who prosecute the defendants in court. The police half focuses on the exciting case load of London Metropolitan Murder Investigation Unit (M.I.U) made up of dedicated officers including recovering alcoholic Senior Detective Sergeant (D.S) Ronnie Brooks (Bradley Walsh), who substitutes booze with food, he is a cop from the East End with a tough past and a big heart. His partner is Junior Detective Sergeant (D.S) Joe Hawkins (Ben Bailey-Smith), a young officer who has come straight from child protection to the murder squad. Their boss DI Wes Leyton (Paterson Joseph) has been through it all and knows the only way to change things is from the inside. Once our police heroes start pounding the streets in the pursuit of their prime suspect by piecing together the clues of each and every heinous crime. They do not stop until the jigsaw is complete and they have enough evidence to make an arrest. But catching the killer isn't always enough, once the crooks are caught and the evidence has been gathered, the Crown Prosecution Service (C.P.S) takes over for the second half and in a tough criminal justice system founded up the belief of 'Innocent until proven guilty' the burden of proof falls on the shoulders of the Prosecutors of the CPS. Fighting furiously for justice week in week out is Senior Crown Prosecutor Jake Thorne (Dominic Rowan), who is supported by the defense barrister turned Junior Crown Prosecutor Kate Barker (Georgia Taylor) and keeping them in check is CPS London director Henry Sharpe (Peter Davison), who steers his office with a steady hand. The CPS team tackle the biggest and most controversial case where life and liberty hang in the balance, These are their stories.