Gerry Standing’s youngest daughter is about to marry a solicitor and she becomes upset after hr father interrogates Robin about his credentials. Sasha Miller is forced to work with her ex-husband, Ned Hancock whilst Gerry receives a visit from an old friend from the past, Ralph Paxton, who has just just been released prison. He wants Gerry to help him solve the murder of his youngest grandson an architecture student called Jake.
Dan Griffin is feeling depressed because his daughter Holly gone to university. The team attempt to improve his spirits by taking him for a ride on a Pedibus in London. They also attempt to solve the murder of Lydia Syson who was strangled back in 2010.
The death of a suspected terrorist, Winston Loveitt is investigated by the team, after his daughter, Ivy, receives an anonymous note saying the MET Police have killed him off. Sasha agrees to go for a dinner with Ned, in hopes of a reconciliation.
After an 80-year-old woman suffering with dementia walks into a South London police station wanting to report a murder, the team soon find themselves investigating the disappearance of police officer Jimmy Hargeaves, who vanished in 1956.
After the body of film critic Oliver Houghton is discovered in the Thames, Sasha Miller has to work alongside her ex-husband Ned Hancock once again.
After a Roman sword is found with traces of blood on it, the DNA is linked to an unidentified, headless corpse discovered near Heathrow Airport in March 2008. The team take a look around a lock-up belonging to the owner of the sword who died of a suspected heart attack, also in 2008. After they discover the missing head they begin to look for connections between the original murder and Rix’s death.
UCOS want to talk to a Turkish girl who is found working illegally in Dalston, regarding a unsolved murder from 2009. The landlord of a pub, Richard Gibson, died in a fire and the case had remained unresolved. The team meet the landlady of the pub, Joanna Gibson, who is also Richard's widow. His best friend, David is also someone of interest, especially when the team find out the French champagne he is selling, is actually sparkling wine produced in Britain. Sasha enters the team into a 5-a-side football competition.
As they investigate the murder of interpreter Agnes Bradley, the UCOS team receive a partial DNA match from a teenage boy who once threw a brick onto a motorway. They talk to the boy to try and fond out if one of his male relations could be the murderer, only to find out that his mother was raped and they could be looking for a rapist-turned-murderer.
Ellen Barker is murdered, a cold-crime enthusiast. At her home, a photo of Dan Griffin is found, so he is the prime suspect. The team soon find out the pair were friends. Sasha comes into contact with DCI Grace Mackie, a ex-colleague from their Hendon training, to help them tackle the case. Griffin assumes that the last case Ellen was looking at could lead to clues about her killer, heading to Minchampton, where a woman called Sally was murdered 25 years ago.
A time capsule is dug-up and is found to contain the cassette tape made by murdered schoolgirl Amy Taskerland. It was in 1983 when sixteen year-old Amy was murdered on the night of her school disco. The UCOS team interview Amy's best friend Harriet as well as the current headmaster, Mr Hines. Dan analyses the strange mix of music and poetry Amy had recorded. However he soon discovers that the tape was made for the Queen and was only intended for broadcast in the event of a nuclear war. The team have to unravel whether the possession of the recording had lead to her murder. The team also are aware that Robert Strickland is keeping his own secret from them. To the team he seems troubled and keeps joining them at the pub.