Newly promoted Detective Chief Inspector Kathy Kolla investigates a series of brutal murders on Hampstead Heath. Under intense pressure to find answers, she arrests the unlikely figure of Charles Pettigrew, a failing London publisher who lives alone on the edge of the Heath. Pettigrew's lawyer calls on recently retired David Brock for advice, and soon, unable to resist the pull of investigation, the old colleagues, Brock and Kolla, are at loggerheads...