Georgie Soloway (Dustin Hoffman) is a rock music composer who experiences personal conflicts when trying to track down a man named Harry Kellerman, who had been spreading outrageous lies about him. Soloway is a rich and successful man who lives in a fancy penthouse apartment and seemingly has everything, but he's beginning to think he is losing his mind; he can't sleep, women he's dated are rejecting him after getting calls from the mysterious "Harry", and he fantasizes committing suicide by leaping off his balcony. Regular visits to his psychiatrist are not helping. At night he struggles with insomnia and can only sleep when his long-suffering accountant comes over and reads his earnings statements to him. When he does sleep, he dreams again about jumping to his death.
As Georgie tries to make sense of his life, he thinks back on his experiences. Although Georgie is a love song writer, he's never had a successful, lasting relationship. His first love, Ruthie, broke up with him after he got her pregnant and she had to have an abortion. He later met a kind waitress named Gloria whom he also got pregnant; he married Gloria and they had two children, but then he cheated on her and she asked for a divorce. More recently, he met an aging actress named Allison (Barbara Harris) who had just miserably failed an audition for a rock musical. Alison turned out to have a lot in common with him, including a failed marriage and thoughts of suicide. When he learns it's her birthday, he takes her for a ride in his private plane and they spend one romantic evening together.
Georgie visits his aging father, who runs a small restaurant and has always had a dream of opening a bigger place. Georgie asks him why he doesn't move elsewhere and open the large restaurant of his dreams with the checks Georgie has sent him, instead of always sending back the checks. His father explains that he is starting to suffer the effects ofarteriosclerosis and that it's too late for him to open a new restaurant now, because he will soon die. Georgie goes for a ride over New York City in his private plane and looks for the cemetery where his father said he wanted to be buried. Then he tries to call first Ruthie and then Alison on the sky phone in the plane. Neither of the women recognize his voice, so he hangs up, but not before revealing that he himself is "Harry Kellerman."
At the end, Georgie is shown crashing his private plane into the buildings of Manhattan, then cheerfully skiing away with his psychiatrist.