A Death in the Family (S09E01)

Jack reveals his intention to depart from the team, but before Sandra, Brian, and Gerry can probe into his motivations, Stephen Fisher, a figure from Whitehall, arrives with a mysterious case tied to a century-old unsolved murder of a woman. With just 24 hours on the clock to crack the case, the team races against time, trying to uncover the truth behind Jack's unexpected choice while also working to convince him to stay.