"Rabbit Hole" by David Lindsay-Abaire

Rabbit Hole is a play focusing on a couple, Becca and Howie, trying to cope with the death of their only child, a four-year-old, in an auto accident, while Becca’s well-meaning mom and off-kilter sister attempt to lift their spirits, each in her own inimitable way. The couple's lives are further complicated when the young driver who killed their son contacts them seeking closure as well.
2007 Pulitzer Prize winner for Drama and it is being turned into a movie staring Nicole Kidman.