When a nurse downloads an app that claims to predict the moment a person will die, it tells her she only has three days to live. With the clock ticking and a figure haunting her, she must find a way to save her life before time runs out. In a teenage party, a group of friends download the app Countdown that predicts when the user will die. The teenager Courtney sees that she has just a couple of hours to live and does not accept the ride of her drunken boyfriend Evan. She walks home but she is killed by a supernatural creature when the timer in her cellphone reaches zero. Meanwhile Evan crashes his car at the same time of her death and he goes to a hospital where the nurse Quinn Harris works. Evan discloses that he is afraid to go into surgery since the app Countdown predicts that he will die at the same time of the surgery. The doctors and nurses of the hospital decide to download the app and Quinn learns that she has only three days of life. When Evan mysterious dies in an accident at the hospital, Quinn buys a new cellphone and finds that the app is also installed. When she meets Matt Monroe at the parking lot of the store, she learns that his death is predicted for a couple of hours before her and they team-up to look for a means to break the curse.