A man accused of opening fire on a crowd from a multi storey car park, and killed a policeman, is claiming his innocence. Boyd's colleagues question his loyalties when he seems unwilling to re-investigate. As DC Mel Silver digs deeper, she discovers some disturbing truths about her boss.

Boyd struggles with his past while continuing the investigation on a mass murderer who was also guilty of killing his close friend. Are the Gunman's claims of innocence true? As the team investigate it looks as if someone else may have been involved.

When a convicted killer is cleared at appeal for the murder of his adoptive father ten years previously, Boyd is not convinced that the man is innocent. But the only way to find out is to track down the rest of the family - and with a big inheritance at stake, both parties appear to have a lot to hide..

Following the murder of Mark Lovell's cousin, the team establish that Mark has a watertight alibi, and the search for the real murderer narrows down to the remaining family members.

Their investigation into the two remaining family members is further complicated by the discovery of drug dealing and involvement in the witness protection scheme.

A recovered memory therapist alerts the CCS to a care home regime of sexual abuse of young boys and a suspected murder. Her client who revealed all this in a therapy session goes missing and the team strongly suspect he has gone on the hunt for the man who abused him and murdered his friend.

A mummified body sends the Cold Case Squad back to the sixties and to a Notting Hill house which had been featured in a film as the location for a murderous fight between gangsters.

Renovation works at the house in the present day reveal more bodies behind the walls.

The film starts to appear not so fictional after all. Things get even more complicated when Spencer tells Boyd that he and his family lived there when the events took place.

The gangster responsible for the bodies behind the walls in the Notting Hill house is still active and the unearthing of past events provokes more murders and an international turf war.

Spencer's family history is the key to unravelling the mystery.