When a new witness comes forward with information about the violennt murder of a brilliant young doctor, the team uncovers evidence of her unhappy past: a possible stalker, a tutor who was suspiciously close, and the husband of a patient who died under her care. Dan is depressed because his daughter has left home for university

An 80 year old woman with dementia walks into a police station to report the 60 year old murder of her husband, a London bobby. The official report says he fell into the river, but the team's investigation uncovers old secrets, After Steve's teenage son is arrested for buying weed, Steve encounters the ex-wife he hasn't seen in 10 years.