Retired archaeologist Judith Potts's (Samatha Bond, Home Fires) peaceful evening in Marlow is shattered when she witnesses a brutal murder. With the local police led by newly promoted DS Tanika Malik (Natalie Dew) reluctant to believe her story, Judith teams up with local dog-walker Suzie (Jo Martin) and unfulfilled vicar's wife Becks (Cara Horgan) to investigate.