Mary secretly takes his patients, but one death doesn't go as planned.

Mary makes a horrifying discovery, sending Annie on a dangerous collision course with Frances. Meanwhile, Ben attempts to reconcile with Mary, and Des becomes attached to a difficult patient.

Ben asks the police to look into Frances, forcing Mary and Des to put their assisted deaths on hold with devastating consequences. Meanwhile, Des and Lucy's relationship is brought to a head, and Naomi's downward spiral continues.

Mary and Ben devise a trap for Frances using the hospice, as Ben uses his connections to investigate her past.

Following a murder at the hospice, Mary and Ben have 24 hours to convince the police that Frances is the real killer.