After a freak car accident kills her husband and two daughters, main character Cristina Peck (Naomi Watts) donates her dead husband's heart to a mathematician (Penn) whose own diseased heart is killing him. Drawn to Cristina in gratitude and empathy, he and a born-again Christian ex-convict Jack Jordan (del Toro) find their lives intertwined with Cristina's, as the three of them experience and share their despair, hope, and change. Redemption in the face of irreplaceable loss underlies and weaves itself through the film, giving the viewer a tangible sense of the worth of life.