Season 4, Episode 5:
The team reinvestigates the 1950s murder of Frederick Tully, a young wages clerk at Battersea Power Station. Patrick Dunne was hung for Tully's murder, but his granddaughter Hannah is waging a campaign to get Dunne posthumously pardoned. The discovery of a suitcase of cash in the attic of the former Tully home sheds new light on the case, revealing a possible blackmail plot. And when Sir Edward Chambers, the key witness against Dunne, retracts his evidence, the team has reason to question the outcome of the original investigation.