Although Lucy Nash has hoped that Cameron Hall will travel back in time to attend her high school graduation, she never dreamed his motivation to come back would be less about seeing her graduate than about saving her life: he has learned that she was murdered days before the ceremony, and he wants to take her to his time in order to protect her from the killer and try to figure out who he or she is in order to prevent it from happening. As they work together with the people that Cameron trusts with his time travel secret to solve the mystery, both he and Lucy are realizing their plan to be together despite a wide age gap in the future might not be a realistic one. Can they find and stop Lucy's killer - and if they do, will the solving of the mystery mean the final goodbye for Lucy and Cameron?