Helen Phillips is a young engineer struggling with the heartbreak of the recent suicide of her husband on the cusp of his greatest professional triumph-a time machine prototype shrouded in secrecy. Helen's grieving is interrupted when she wakes up one morning, disheveled and panicked, her memory damaged. The phone rings and a voice, sounding uncannily like her own, warns that she's in danger. Soon Helen is on the run from unknown pursuers while she follows a trail of clues she seems to have left for her to find. She quickly realizes that she has actually traveled thirty-six hours back in time, but why?