The Bill: Invisible Man

First of two parts. DCs Webb and Banks investigate when the body of a young man is fished from the Thames. The dead man is identified as Jake Evans, and the detectives discover that he had been volunteering at a homeless shelter. Initially suspicion falls on the deceased's fiancee, who had argued with Jake a few days before he died. But after Webb spends a night on the street befriending some of the homeless people Jake knew, the officers realise that the community is living in fear of someone who may have have had a hand in Jake's murder - but who?