Mary Harris believes in her work. “Death gives life meaning,” the secret euthanasia provider (Caroline Dhavernas, “Hannibal”) declares in the trailer for Season 2 of Lifetime’s “Mary Kills People.” “Life is precious because of it.”

So you can see why Mary is so shaken when Olivia Bloom (Rachelle Lefevre, “Under the Dome”) asks Mary to kill her perfectly healthy husband. “That’s not what I do,” Mary explains. “How old’s your youngest?” Olivia counters. “Around 12?” The implication is clear: either Mary kills Olivia’s spouse or Olivia will go after Mary’s family.

“It’s the line we don’t ever cross,” says Mary’s work partner, Des (Richard Short, “Vinyl”). They help the terminally ill die with dignity; they aren’t murderers for hire. “What other choice do we have?” Mary replies. She’s willing to cross any and every line in order to protect her daughters.

Created and showrun by Tara Armstrong (“Private Eyes”), “Mary Kills People” returns March 12.