Christian Bale plays Patrick Bateman, a 27 year old living in the late 80's working at his fathers wall street firm in the mergers and acquisitions division. He lives in a high rise alone but has a girlfriend (Reese Witherspoon) that is constantly making wedding plans. He and his colleagues spend most of their time together trying to one-up each other in the vanity department debating who has the better suit, better business cards or even better restaurant reservations. They hang out together at nightclubs doing lot's of cocaine.
Patrick is really into his appearance spending way to long in the shower with moisturizers, cleansers or whatever the latest skin care fad is. He is very anal about coasters on coffee tables or desks. He has a nice stereo with a very up to date CD collection. Seems to be living the good life, right?
Turns out that he really is a psycho.
For no reason at all he approaches a homeless man and stabs him.
When his coworker Paul Allen (no, not that Paul Allen), gets a better account, Patrick gets him drunk, invites him up to his apartment and while talking about the new "Huey Lewis and the News" CD, whacks him in the face with an ax. He hides all the evidence and goes to Paul's apartment and makes it look like Paul took a trip to London.
He meets a model at a dance club and invites her to his place. The next day we see him at his desk playing with a lock of her hair. Later we find her head in his refrigerator.
He meets up with a prostitute and invites her and another call girl to his apartment. They make a wild sex video and discuss the song stylings of Phil Collins before and after Genesis. Just when the two are about to leave, he says we're not done yet as he goes to his drawer to get some tools. (hardware, not sex toys). They don't show what he does but we do see them leaving, crying.
He invites his secretary over and makes a few advances to her but just as he's about to shoot her in the back of her head with a nail gun, his fiancee calls. He tells the secretary she should leave because he doesn't want to hurt her. (She's thinking emotionally, he's thinking physically.)
The next day he has another old friend over at Paul's house along with the same prostitute he earlier picked up. Their foreplay involves discussing the greatness of the new Whitney Houston album. They get in bed together but the prostitute decides to leave before she gets hurt again. Suddenly the old friend starts screaming and blood appears everywhere on the sheets. The prostitute screams and starts running all through the house. Everywhere she turns or door she opens, she finds corpses and blood spattered all over. She finally finds her way out of the apartment and runs down the hallway screaming and banging on other apartment doors. He takes off after her completely naked carrying a chain saw. (Wait, I'm wrong... I think he was wearing socks). As she runs down the fire exit he waits up top with the chain saw still running. Timing it perfectly, he drops the chain saw down to the bottom, hitting and killing her.
The next day he meets Reese Witherspoon and tells her he's a psycho and doesn't want to get married. She causes a scene at the restaurant and he leaves.
Okay, now it starts getting strange...
He goes to a cash machine and as he's taking out his money a kitten appears. He picks up the kitten and a message on the cash machine reads... FEED ME THE KITTEN. He puts a gun to the kitten then an old lady walks up and asks him what he's doing. He shoots and kills her. Suddenly, the police show up and he has a shoot-out with them, blowing up their patrol car and killing them. He runs around town killing anyone he sees. He goes up to his office but is being watched by a police helicopter outside. He calls his lawyer and confesses everything.
The next day he goes back to Paul Allen's apartment but it is all cleaned up and unfurnished. It is for sale and the Realtor asks him to leave because he's acting weird.
He calls his secretary from a pay phone telling her he's not coming in that day. She takes that opportunity to search his desk and finds a book with his sketches and scribbles of women getting tortured.
He goes to a business lunch with his coworkers and sees his lawyer. He asks the lawyer if he got the message. The lawyer thought it was a joke. Patrick tries in vain to convince the lawyer that it is the truth and that he really killed Paul. The Lawyer says it can't be because he just had lunch with Paul in London a few days earlier. Patrick goes back to his lunch with his other co-workers debating insignificant topics.
Turns out (in my opinion) that Patrick had one too many cocaine induced dreams and actually started believing that he had done all these things.