As Sam continues her forensic investigation into the two deaths, the police make an arrest but soon realize they have the wrong person in custody when a crucial piece of evidence is uncovered. Sam discovers the true identity of the person behind the deaths but rather than tell the police, she decides to let him to turn himself in. Unfortunately, this leads to a tragic result. In her personal life, Sam and Peter Ross renew their long-ago romance.

The team investigates two deaths, the first a suicide where someone jumped to their death and the second where a paranoid schizophrenic dressed as a vicar goes on a rampage stabbing innocent bystanders. Their suspicions are aroused when they learn that both men were receiving treatment at the same clinic, January House. Leo assists the police in their investigation of a building society employee who is forcibly taken from his house and subsequently found dead in his own car. Harry is asked to perform an autopsy and provide a second opinion in the death of a young woman. The death was ruled a suicide, but the mother refuses to accept the verdict.

The Director of January House tries to take his own life on the clinic grounds and the pathologists suspect they may have a case of adulterated prescription medication. Harry's repeat autopsy reveals that the young woman was also under medicated, but she had no contact with the clinic. The police suspect the wife in the case of the building society employee and Leo sets out to disprove her time line.

The team follows the trail of the people traffickers, and has to find any remaining survivors before a highly contagious disease breaks.