In 1958 New York, devoted wife and mother Diane Arbus (Nicole Kidman
) is torn between love for her husband and children and her profound need to create and explore. She finds her talents and dark obsessions are profoundly at odds with the conventional life she leads.
she becomes intrigued by her new neighbor, Lionel, (Robert Downey Jr.), who is bundled up in a coat and hat, his face obscured by a scarf and mask the first time she catches sight of him. Over the next two weeks, she hears his footsteps on the stairs, music playing from his attic apartment, and sees a bald visitor who dashes upstairs but returns visibly changed.
While investigating a backed-up sink, Diane traces the problem to a pipe linking their two apartments. She makes her way up to Lionel's ornate door with a camera. However, she doesn't take his photo that night or the next, when he invites her into his home. It's the beginning of an adventure that will take Diane into the underground worlds that have always called to her -- and into a compelling intimate relationship that will transform her life and her art forever.