Season 7, Episode 5
The team reopens a four-year-old case when graffiti appears around London by an unknown person claiming to have murdered a celebrated street artist. Originally part of a gang, the victim went solo when he received support from a wealthy art patron, leaving the detectives suspicious of his resentful former crew members. Meanwhile, Brian signs up to a social networking site to chart a lawman's gritty life, much to his colleagues' displeasure.
A motley crew of retired police officers re-opens troublesome cases that were never laid to rest.