The majority of the movie takes place in the alternate version of the day in which Samantha dies. Ian wakes up to find himself reliving the same day, and begins frantically trying to change the outcome. He tries to avoid the argument that preceded Samantha's death, and also tries to convince her not to take a specific taxi that he believes leads to her accident.
During this time, Ian is able to see the impact that Samantha had on those around her and how much she meant to him. He also confronts some of his own personal shortcomings and regrets. As he continues to attempt to alter events, he begins to feel a sense of hope that he may be able to save Samantha.
However, each altered version of the day ultimately ends in Samantha's death, as fate seems to intervene in unexpected ways. Ian eventually learns that there are some events that are beyond anyone's control, and that he must learn to accept and come to terms with Samantha's death.
The film explores themes of love, loss, regret, and the power of hindsight. The performances by lead actors Jennifer Love Hewitt and Paul Nicholls are praised for their emotional depth and authenticity.