Mit : David Mitchell, Anna Maxwell Martin,

With new information about Chief Constable Ziegler, John is sent back to the police station to get closer to DI Russell Carter, his brother's new partner who mysteriously arrived around the same time that James disappeared. A new case takes John and Russell on a walking tour of Cambridge, where they are faced with a conundrum: why would someone kill a tour guide that they'd only just met? To get closer to the truth about what happened to conspiracy blogger Roger Sinclair, Lucy goes undercover and makes a shocking discovery of her own.