Molly and Liam survive a train crash at the same time that Daniel is investigating a series of apparently unrelated murders. After each death the killer sends Daniel a taunting message, and a new note makes the couple wonder whether the crash was intended to kill Molly.
Recovering from her injuries, Molly works with Sid and Gus, whose interest in dream analysis suggests that her recurring dreams may contain a forgotten clue. She reconstructs what happened before the crash while Daniel searches for the link between the victims.