Season 1 of Mary Kills People premiered on January 25, 2017.

Season 1 follows Dr. Mary Harris, an overworked single mother and ER doctor who also moonlights as an underground angel of death, working outside the law assisting patients who want to die on their own terms. So far Mary has managed to stay under the radar but business is booming, and her double life is getting complicated.

Season 2 of Mary Kills People premiered on January 3, 2018.

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.

Season 3 of Mary Kills People premiered on May 12, 2019.

In the third and final chapter, Dr. Mary Harris must come face-to-face with her own personal choices, ethics, and demons in a way she never has before. The death retreat is up and running, but its cover as a legitimate hospice is crumbling away and with it the idyllic vision Mary and Des had for continuing their work in quiet secrecy. With Mary’s family and the work she loves in jeopardy once more, she realizes she is finally going to have to put life, with all of its complexities and imperfections, first.