Got a Light? (S05E07)

When a doctor's car plunges into the harbour, the Nemesis is first to respond and Gavin's new partner, Matthew Quinn, dives into the water to pull the man from his car, too late to save him unfortunately. As a series of arson fires are set at properties owned by the deceased doctor, the detectives focus their investigation on one of the doctor's patients who is a serial arsonist. (Prime Video)