It is 1976, and 8-year-old Mary Daisy Dinkle (Bethany Whitmore) is a lonely little girl living in Mount Waverley, Australia. Her relatively poor family cannot afford to buy her toys or nice clothing, and she is teased by children at her school due to an unfortunate birthmark on her forehead. Her father is distant and her alcoholic, kleptomaniac mother provides no support. The closest thing she has to a friend is the man for whom Mary collects mail, Len Hislop, a Greek Australian World War II veteran who lost his legs in combat and has developed agoraphobia.
One day, by pure chance, she decides to write a letter to a man living in New York City: Max Jerry Horowitz (Philip Seymour Hoffman). Max turns out to be a morbidly obese 44-year-old whose various mental problems (including anxiety attacks and overeating) have left him unable to form close bonds with other people. Max decides to write back to Mary, and the two become friends. Over time, Mary's increasingly sensitive questions about the adult world give
Max progressively worse anxiety attacks, and he is ultimately institutionalized. During his time there, Max is diagnosed as suffering from Asperger's syndrome. Now aware of why he has difficulty relating to other people, Max finds a new lease on life and resumes his correspondence with Mary.
The two remain friends for the next two decades, keeping one another updated on various events in their lives. Mary (Toni Colette), inspired by her friendship with Max, becomes a psychologist and marries her childhood crush, an effeminate young man named Damien Popodopoulos who enjoys sewing but fears Mary's sexual advances. Max wins the New York lottery, using his winnings to buy a (literal) life-time supply of chocolate and then giving the rest away to his elderly neighbor, who wastes most of it before dying and leaving the remainder to a cat shelter only to have the owner of the shelter take it all for himself.
After earning her degree, Mary writes a psychological book detailing her communication with Max, in an attempt to dissect Asperger's syndrome. Max is infuriated, having told Mary that he has come to terms with his illness and sees it as an integral part of his personality, not something that needs to be diagnosed and cured. Max ends his communication with Mary, sending her the "M" key from his typewriter. When Mary receives the key in the mail, she has the entire run of the book pulped, ruining her career. Jobless and friendless, Mary discovers that, while she has been focused on her book, her husband has left her for his own penpal, a gay sheep farmer in New Zealand. Mary sinks into chronic depression and alcoholism; although Max decides to forgive Mary and sends her a present in an attempt to reconcile, Mary becomes a shut-in, leaving the box on her porch for several days. Ultimately, Mary decides to hang herself, unaware that she is pregnant.
Just as Mary is about to kill herself, Len knocks on her door, having conquered his agoraphobia to alert her of the package on her porch. Opening it, Mary finds Max's reconciliation gift. It is enough to jar Mary from her depression, and she decides to start her life over again.
A year later, Mary travels to America with her infant son to finally visit Max. Entering his apartment, Mary discovers that the now elderly Max has passed away. Looking around the apartment, Mary discovers that Max has organized the entire ceiling into a detailed scrapbook of his friendship with Mary, composed of all of her letters from over the years, causing Mary to cry tears of joy.
Starring
Bethany Whitmore
Toni Collette
Philip Seymour Hoffman
