The split-second moments that can take a life down one path instead of another form the tantalizing "what if?" in this delightful romantic comedy. London publicist Helen slides between parallel storylines that show what happens if she does or does not catch a morning train back to her apartment. Love. Romantic entanglements. Deception. Trust. Friendship. Comedy. All come into focus as the two stories shift back and forth, overlap, then surprisingly converge.