The Lyell team investigate the clinical shooting of a mother, stepfather and son by the River Malt, to determine who killed this picnicking family and why. The investigation soon turns to the female victim's estranged husband. The couple were in the middle of a bitter and acrimonious divorce, and records kept by the deceased show that the husband has a propensity for violence.
Working on the case is local detective Malcolm Guillam, about to retire and haunted by the death of a young woman near the River Malt ten years ago. When the present day murder brings back memories of the unsolved case, Guillam sees an opportunity to redeem himself. But leading the investigation is DCI Butcher, who is certain the estranged husband is responsible for the murder, and has little time for Guillam's perceived trip down memory lane.
Meanwhile, registrar Amy is advancing in her surgical career when news of the River Malt shooting brings back memories of the same incident that haunts DS Guillam. Attempting to bury her past, Amy is unwillingly pulled back into the same world that caused the death of her friend ten years ago and forced to confront the high-powered people she has been trying desperately to forget.
Silent Witness originally followed the work of forensic pathologist Dr. Sam Ryan, played by Amanda Burton. In 2004, Burton left the series and Nikki Alexander, played by Emilia Fox, joined Dr. Leo Dalton (William Gaminara) and Dr. Harry Cunningham (Tom Ward) on the forensic pathology team. The series was created by an ex-police officer, Nigel McCrery.
Jack is rushed to hospital after collapsing at the scene of a car crash. Thomas discovers that soldier John Sealy may have been exposed to a nerve agent.
Thomas investigates the case of John Sealy, a soldier who died during a military training exercise involving exposure to CS gas. It appears John died from an aneurysm, but when Thomas discovers the trace of a possible nerve agent in his system, the family are desperate for answers.
The Lyell team identify the concrete-encased remains as those of Derek Marshall, survived by his wife Sue and sister Ann. Clarissa traces payments to a cryogenics facility, leading to the discovery of another suspicious death. Lacking any proper documentation, the coroner orders a post-mortem into the cryogenically frozen body. How did they die, and why was the decision made to freeze them?
Teenagers messing around in a stolen car collide with a concrete pillar in a multistorey car park. The joyriders escape, but within the smashed
concrete, the unmistakable form of a skull is revealed. After painstakingly extracting the skeleton encased inside, Nikki and the Lyell team must investigate a suspicious dating back 20 years.
Meanwhile, Clarissa faces a difficult decision regarding her mother’s care.
Nikki determines that Jenny must have died before making contact with the tracks. But when the search for Jenny’s killer hits a wall, her friends at the women’s refuge seek answers. Meanwhile, Thomas’s political ambitions lead him to make friends in high places. Offers are made to open all the right doors for Thomas, but what do they want in return?