Troubled by bouts of sleepwalking and disturbing nightmares, graduate student Sarah Foster goes to her university's sleep research center for help. When she wakes up after her first night of being monitored, the world she lives in seems to have changed in subtle, Twilight-Zone-esque ways.

In fact, every time she goes to sleep now, she wakes up in a slightly different version of her world. With the help of sleep researcher Scott White, she tries to work her way back to the reality she started in. But when they finally succeed, it's revealed that Sarah's world is not what she thought at all.