Sixteen-year-old Mehreen is overwhelmed by her anxiety and depression, and she doesn't believe anyone in her life will understand if she tries to talk about it. She's been thinking about suicide for a while when she discovers a website called MementoMori.com. The site matches people with partners and assigns them a date on which to end their lives, together. Mehreen is partnered with Cara and Olivia, strangers dealing with their own struggles. But as the girls get to know one another in preparation for their "date of termination" they find themselves developing a strong bond—even becoming friends. For the first time, they're each able to share their darkest secrets with people who won't judge them. They realize that, with the right support systems, life is worth living after all. So they decide to abandon the suicide pact. Except the website won't let them stop. As their assigned "date of termination" draws nearer and MementoMori continues to manipulate them, the girls will have to rely on one another to survive.