At a teenage party, a group of friends download the app Countdown that predicts when the user will die. Courtney sees that she has just a couple of hours to live and does not accept a ride with her drunken boyfriend Evan. She walks home but is killed by a supernatural creature when the timer in her cellphone reaches zero. At the same time she dies, Evan crashes his car and he goes to a hospital where 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 in the store's parking lot, she learns that his death is predicted for a couple of hours before hers and they team up to look for a way to break the curse.