Retired archaeologist Judith Potts lives alone in a faded mansion in the peaceful town of Marlow, filling her time by setting crosswords for the local paper. During one of her regular wild swims in the Thames, Judith hears a gunshot coming from a neighbour's garden and believes a brutal murder has taken place.

• Samantha Bond
• Jo Martin
• Cara Horgan
• Natalie Dew
• Mark Frost
• Tijan Sarr
• Daniel Lapaine
• Mark Fleischmann