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.

Still reeling from the untimely death of one of their patients, Mary and Des decide to take a break from their partnership. While Des grapples with helping a 21-year-old man suffering from terminal cancer, Nicole convinces Mary to take her to a patient session in order to experience firsthand what it’s like to help someone end their life. Mary must also deal with the repercussions of threatening Olivia who now knows that Mary was responsible for killing her brother Grady. When Mary realizes that Olivia will not stop blackmailing her until she agrees to kill her husband Travis, she is forced to make an impromptu plan that collides with Ben’s undercover investigation in an unexpected way. Meanwhile, as Jess navigates the throes of her first love, Naomi makes a shocking discovery.

Mary and Ben join forces; Travis reveals a crucial detail about Ben's investigation.

Des worries that he and Mary may have crossed a moral line; Ben's investigation is jeopardized.

Ben forgives Mary; Mary and Des move forward with the death retreat.

Mary decides to wear a wire; Des and Nicole prepare for Brendan's death.