Last call (2012)

A woman must solve a riddle over the phone to save a stranger's life. In the middle of the night, Kristen is awakened by a phone call from a stranger asking for her help. She is given half an hour to solve a riddle that could ultimately save the stranger's life. Skeptical at first, she reluctantly plays along, but as the countdown begins, it becomes dangerously clear that this is not a game...