This Will Bother You

S21, E31: Margaret Barnes falls down a flight of stairs during a tussle with an increasingly harassed DS De Costa, who has become convinced she's being stalked. DI Manson returns to Sun Hill, and PC Hemmingway agrees to a date with nurse Nick, only to leave him in the lurch. DS Nixon and DC Perkins find themselves in a room full of venomous snakes, while Insp. Gold faces an ordeal of a different kind as she prepares to start chemotherapy.