In season 2, Mary plummets deeper into the criminal world as she searches for a steady supply of pentobarbital, the highly regulated and highly lethal "death drug." As she becomes more entangled in her illegal work, Mary continues to risk her family and career as she tries to keep her worlds separate. But when the mysterious Olivia Bloom approaches Mary and her partner Des with a lethal request, and when Mary crosses unexpectedly with Detective Ben Wesley, she realizes her secrets can only be hidden for so long.
Des is happy to reteam with Mary following his stint in prison - but when a routine case leads to a devastating outcome, Mary questions whether she was better off fighting the good fight without him in control and unchallenged.
When Olivia attempts to blackmail Mary, she is drawn deeper into a deadly game of cat and mouse that has a surprising connection to Ben.
Mary and Ben decide to join forces and hide Travis at Ben's secluded trailer. But when Travis reveals a crucial detail about Ben's investigation, Mary is forced to reconsider their alliance.
Following the disappearance of Travis, Des worries that he and Mary may have crossed a moral line from which they can never return. After jeopardizing Ben's investigation of Olivia, Mary tries to make amends, which has repercussions for a patient in dire need.
All seems well for Mary, Ben has forgiven her, and she and Des have decided to move forward with the death retreat. The only nagging concern for Mary: her daughter Jess hates her and doesn't believe a word out of her mouth.
Mary decides to wear a wire in order to help Ben take down Olivia, but when their plan takes an unexpected turn, Mary must reconsider her allegiance. As Des and Nicole prepare for Brendan's death, Des faces crippling self-doubt about his dream.