Newly-wed Rachel struggles to adjust to living with Sean. Admitting their marriage is over, Janet and Ade put their house on the market, planning to split when it sells. When she is called to a crime scene, Janet discovers the severed head of 75-year-old Eunice Bevan at the bottom of the stairs in her home, with her bedridden husband Joe lying upstairs. Tracing their relatives becomes crucial, but as Joe becomes more lucid in hospital, their daughter Helen's alibi starts to fall apart.

Rachel's moment of indiscretion threatens to come back and haunt her when Sean takes a phone call from her recent one night stand. Janet forces Ade to move in with his new girlfriend and asks her mum Dorothy to take his place. The team investigates the brutal murder of a wealthy man whose double life left him vulnerable to exploitation. Could his son really be the prime suspect?