I watched this movie this winter. It's really super.
Snow Cake is a film about a friendship between a man and a highly functional autistic woman. Her daughter had been hitch-hiking and the man, Alex (Alan Rickman--he played Snape in Harry Potter, I think), had picked her up. They got into an accident on the way, and the daughter, Vivienne, died. He goes to talk with her mother, Linda (Sigourney Weaver), who convinces Alex to stay with her. One of the things she cannot stand is taking out the garbage and after a bit of persuasion he agrees to have a small stay with her. She becomes attached and he ends up staying with her for a long time. Throughout the movie, he develops a relationship with the neighbor (Carrie-Ann Moss) and has troubles with a local policeman who thinks he has unearthed a dark secret from Alex's past. In the end, Alex is changed and leaves Linda to be alone. She too has overcame many challenges.
It's a very good movie and I recommend you see it. : ]