A young nurse named Quinn Harris downloads a popular app that claims to predict exactly when a person will die, only to discover it ominously heralds that she has just three days left. Initially skeptical, Quinn soon starts experiencing unsettling occurrences that suggest the countdown is real. Desperate to find a way to extend her life, she researches other app users and discovers several have tried to outsmart it, only to meet grim fates. She learns that breaking the user agreement could potentially save her, setting her on a frantic race against time.

As Quinn seeks help, she forms an unlikely alliance with Matt, another app user with a similar countdown expiry. Together, they encounter a tech-savvy priest and delve into the app's origins, finding links to sinister and supernatural forces. Each clue uncovers more about the app's dark power and those who created it. Racing against their own clocks, Quinn and Matt must find a way to break the curse before their time runs out while facing life-threatening dangers and uncovering frightening truths along the way.