Sally Jansen was NASA's leading astronaut, until a mission to Mars ended in disaster. Haunted by her failure, she lives in quiet anonymity, convinced her days in space are over. She's wrong. A large alien object has entered the solar system on a straight course toward Earth. It has made no attempt to communicate. Out of time and out of options, NASA turns to Jansen. But as the object reveals its secrets, Jansen and her crew find themselves in a desperate struggle for survival -- against the cold vacuum of space, and something far, far worse...