21 Grams is an American drama movie directed by Alejandro González Iñárritu and written by Guillermo Arriga. It stars Sean Penn, Naomi Watts, Benicio del Toro, whose lives are connected when del Toro's character Jack Jordan kills the husband and two daughters of Watts' character Cristina Peck in a hit-and-run road accident. His heart is transplanted into Penn's character, mathematician Paul Rivers.