Dr. Mary Harris has a secret – beneath the surface of being an ER doctor and loving mother, Mary is also Dr. Death, helping terminal patients end their lives. She and her partner Des have been operating covertly for almost six months but a series of unforeseen circumstances, beginning with the assisted death of superstar football player Troy Dixon goes wrong, conspire to tear Mary down. Meanwhile, her greedy ex-husband Kevin introduces her to his new girlfriend, she discovers that her 15-year-old daughter's wild BFF is into heavy drugs, and Mary ends up seducing a patient who is not who he seems.

After being intimate with Joel, Mary has second thoughts about ending his life; a client's son pulls a gun on Des; Kevin's relationship with a new woman gets intense.

Mary confronts Ben; Grady blackmails Mary into helping him break a patient out of the hospital; Ben and Frank get a new lead.