When DCI Janet Chambers (Connie Hyde) goes into labor, Commander Clare Blake takes charge of the investigation into the death of a two-year-old girl found on the site of a now abandoned psychiatric institute. The girl has been dead for several years, but her body had been stored in a tightly sealed drum and is well preserved as a result. She also has a cross branded onto her chest. The pathologist's report is inconclusive, so the team start to check medical records of former patients.

Eric Thornton and John Littlewood figure prominently in hospital files, but when it's confirmed that Littlewood has died, the police focus all their effort on Thornton. A dark history of mental problems and violence related to them, Thornton stands out as the prime suspect in the girl's murder, but when his own mother (Celia Imrie) is murdered in cold blood, James isn't convinced that Thornton is responsible for either death.