In high school, Leah and her volatile best friend Christian lorded over the volleyball team. They weaponized their friendship in the way only teenage girls can, until an enigmatic new girl named Corrie arrived-a transfer student who was found leaving an empty mansion in town with a bleeding hand and no memory of how she got there.

Sneaking in to that same mansion to celebrate a volleyball victory, the girls found that whatever happened in the house stayed in the house. Wounds magically healed, haircuts grew back once they left. So they kept going back, daring each other further, to hunt one another with scissors, to jump off the balcony at paralyzing heights. But as the games they played got ever more dangerous, Leah remained untouched by the house's magic. Desperate to hide that she was different from the others, Leah begged her twin Laura to impersonate her for one night, knowing that whatever happened to Laura would have no lasting physical consequences. But the house could not be deceived. One girl was lost that night, and another girl already disappeared in a game that went too far.

Now, 20 years later, Leah is pregnant, and convinced she's having twins despite the fact that only one baby shows on the ultrasound. When an estranged friend from Leah's past reaches out with a theory that might change everything they've held true, Leah is thrust back to the house, desperate for answers about her past, her present, and the pregnancy that convinces her yet another girl has been lost-this time, a phantom daughter of her own.