Mary Kills People

Five months after Mary and Olivia evaded the police in the carwash, the case against Mary has been shelved and Olivia is out of her life. Mary now operates Joy's – a secluded hospice where she and Des can tend to terminal patients without fear of discovery – and is expecting a new baby. Things are seemingly ideal, but Mary is frustrated by Des's "system" and the small number of people she's permitted to help, and she's been secretly seeing terminal patients on the side. In Mary's mind, it's a risk worth taking, but her worst fears are realized when one of her outside deaths is interrupted by a witness, a woman with a dark secret of her own. And unbeknownst to her, a young detective starts looking into her involvement with the patient's death and approaches the former lead detective on Mary's case for more information – Ben.

After coming clean to Des about her close call with the police, Mary promises to never put herself or the hospice at risk again. But Mary's vow to keep her head down is complicated when Frances – the witness from Gail's suicide – turns up asking for a favour. Not wanting to upset someone who can potentially put her in jail, Mary joins her to meet Dorothy – an elderly woman with cancer and a prospective patient for the hospice. Meanwhile, following a fiery night of revenge on an ex's car, Jess realizes something is off with her old friend Naomi, whose trademark wild behavior has become more unstable in their time apart.

Believing that Frances killed Dorothy against her will, Mary and Annie take it upon themselves to remove Frances from her job at the hospital. Meanwhile, after having tipped Mary off about the new detective looking into the hospice, Ben struggles with impending fatherhood and letting himself be drawn back into Mary's orbit. Back at the hospice, Des grows closer to Lucy – a terminal yet lively patient – and struggles with taking the lead on a death. The real danger is revealed when Frances kills Leah, a non-terminal patient, and frames Annie for the crime – showing just how far she'll go when cornered.

Leah's death pushes Mary to come clean to Nicole about Frances. At Ben's insistence, they agree to stop killing people at the hospice until the heat is off, which leaves Des in a difficult situation with Lucy, who he's promised to kill that day. Ben attempts to sway Detective Hull's investigation away from Mary and onto the real target – Frances – without tipping his hand about his relationship with Mary. Back at the hospice, Mary is forced to watch one of her patients die an excruciating natural death, causing her to question what risks she's willing to take for the good of her patients. Meanwhile, a near-miss with Naomi leaves Jess fearing for her friend's deteriorating mental state.

Knowing Hull is watching both Mary and Frances, Mary and Ben enact a risky plan to set Frances up by inviting her to work at the hospice. Their plan is complicated, however, when Detective Hull learns about Ben and Mary's romantic relationship. Frances arrives at the hospice with her father as a prospective patient, and Mary has an unexpected opportunity to learn how her adversary came to be. Meanwhile, Lucy decides she wants to spend her few remaining days with Des, but a turn for the worse drives them back to the hospice with a devastating conclusion. Things come to a head for Jess when Naomi requests that her friend do for her what Mary has done for so many.

Following a murder at the hospice, Mary and Ben have 24 hours before police have the autopsy results – and an iron-clad case to put Mary behind bars for good. Mary thinks Frances's father might have the information they need to turn the investigation onto Frances, and uses him to their advantage. But things are complicated when Mary learns Naomi wants to take her own life, and together with Jess they have to convince her that life is worth fighting for. With Mary sidelined, an emotional Des makes a rash play to bring Frances to justice on his own. Mary, however, comes to realize that turning herself in may be the only way to truly bring Frances down – consequences be damned.