Sixteen-year old Cassie Renfield has seen the mark since forever: a glow around certain people as if a candle were held behind their back. The one time she pointed it out taught her she shouldn't do it again, so Cassie has kept quiet, considering its rare appearances odd, but insignificant. Until she watches a man die. Mining her memories, Cassie realizes she can see a person's imminent death. Not how or where, only when: today. Cassie searches her past, her philosophy lessons, even her new boyfriend for answers, always careful to keep her secret. How does the mark work? Why her? Most importantly, if you know today is someone's last, should you tell?