It's been eight months since Mary and Des framed Grady, their drug dealer, for the deaths of their patients. While Des has been serving prison time to protect his partner, Mary's been managing surprisingly well on her own – she's found a new supply of pentobarbital in Mexico, her business has continued to thrive thanks to Annie's ability to source terminal clients in need, and her ex-husband Kevin has moved in and taken on half the parenting duties following a messy break-up with Louise. Though Jess still suspects that her mother is hiding something, Mary has been working diligently to keep her professional and private lives separate. But secrets can only be hidden for so long when Olivia – a mysterious woman with a connection to Mary and Des – comes to them with a deadly request.