I watched this movie expecting some kind of a horror/thriller from most of the comments here. Of course the basic story has quite some resemblances of the famous "Psycho" but I think that this movie is far more into the psychological level and less into thrills and chills. Thats why I now get some of the negative remarks because if you want to get a psycho axe wielding maniac and his rotten mom you sure will be disappointed by nice guy Leon and his pretty boring doll.
If you just watch Pin for what it is and that to me is a kind of apsychological drama, then it makes much more sense and has some interesting insights. The story revolves around two kids Leon and his Sister Ursula who grow up in a very conservative upbringing. Their mother a 60s cliché of a cleaning obsessed house woman and their father a doctor whom his kids call "Sir" and who teaches them several things through an anatomical doll using ventriloquism. The doll named "Pin" becomes a part of their lives and especially Leon becomes attached to it also talking to him in his fathers absence. Years later their parents die in a car crash and Leon and his sister start living on their own. From here on Pin becomes Leons Alter Ego and kind of a family member ... the downward spiral picks up pace and troubled Leon who desperately tries to keep his "family" together by keeping Ursula from other peoples influences starts going over the edge.
Ursula know about Leons mental state and plays along with his schizophrenic role play and the Pin doll which Leon gives his voice just like his father did. She doesn't want her brother to end in a sanitarium, realizing too late that her playing along just makes things worse.
The movie is very slow and the deterioration of Leons mental state is not thrilling, everything is shown in kind of a normal way because thats what it is for Leon. People die in this movie but its not for thrills and especially the ending shows that "Pin" is rather a drama than anything else. If you are interested in a psychological study in a "Psycho"-like set watch this movie, if you want corpses, thrills and scary horror dolls this sure is the wrong movie for you.