Nineteen year-old Johnny Dart leaves home one night after arguing with his parents--to locate the best friend of his sister. He needs to talk with her as the only other witness to his sister's death, five years since, when she fell over a cliff on a picnic. Haunted by the thought that he might have saved her, Johnny is also convinced his parents and others think it should have been he, rather than his sister, who died.

He shows up drunk at the home of the friend's parents, only to find that she has moved out. In his nighttime wanderings he encounters a disoriented old woman on the streets and follows her home to a dilapidated and disheveled house which, it turns out, belongs to her, though since she suffers from Alzheimer's disease or a related syndrome, has lapsed into extreme disarray and disrepair. He ends up staying to care for her for several days, during which he also locates the old friend.

In caring for the old woman and conversing with the young woman, Johnny manages to come to terms with his own past, the pain of his own losses, and agrees to talk with his parents and a counselor and reorient himself to the present. In the process he learns a great deal about himself, about how he has projected his own fears and guilt, and how caring for another person can release him from crippling obsessions with his own past.