There are two stories caused by two major blackmails in The Big Sleep. The first story is developed around the investigation of a blackmail General Sternwood received from Arthur Geiger. Philip Marlow, a hardboiled detective hired by Sternwood, goes directly to Geiger's rare bookstore and then follows Geiger to his house. Marlow then finds Geiger is shot dead and Carmen, Sternwood's daughter, is drunken inside the house, posing in front of a camera. So what happened in the house? Is Carmen a covergirl or something else? And where's the film roll since it's not in the camera?
Vivan, Sternwood's daughter, goes to see Marlowe with some nude pictures of a woman and these pictures offer an important clue to Marlow becuae the woman on those pictures is Carmen. Tracing the blackmailer who has Carmen's pictures, Marlow is led to Joseph Brody's apartment. Talking to Brody, Marlow finds out Brody wants to take over Geiger's porn business, but he denies killing Geiger. Ironically Brody is shot by Geiger's lover. Now Mr Sternwood's case is closed and Vivan meets Marlow in order to give him his check. Their meeting leads to the second story.
Marlow's professonal sense tells him that Vivan is hiding something from him. Regan, Vivan's former husband, have disappeared for a few months and it's said that he ran away with Eddie Mars's wife. Marlow starts from Mars' casino. However, Marlow is unable to get any information about Ms Mars from Mr Mars. Harry Jones, who knows where Ms Mars is located, finds Marlow and tries to sell the information to him. Canino, Eddie's boy, poisoned Harry before Marlow's able to make the deal with him. Now it seems the clue is cut off, but the girlfriend of Harry, Agnes, is able to finish the deal with Marlow. Marlow then drives to the auto shop where Ms Mars is held. In the shop Marlow is knocked out by Canino. When he wakes up he sees Ms Mars and Vivan.
After a long talk with Vivan, Marlow figures out what's bothering Vivan. Marlow and Vivan then return to Geiger's house. Fallen in the trap created by Marlow, Eddie is shot by his own boys. Marlow then reports to the police like this: Eddie killed Regan although he knows it's Carmen who really killed Regan after being spurned. The ending is romantic when Vivan challenges Marlow by saying, "Nothing you can fix."
The plot of the movie is not easy to follow because it's a complex story and have several herring (something that draws attention away from the central issues) characters. For example, Geigle appears dead on the floor and his death is still a mystery. It is hinted that Taylor killed Geigle but the motives are never shown. Carol kills Brody for his "lover" Geigle without any background introduction and hints. These characters are portrayed in a very minor way, but they offer clues to Marlow and keep the movie going. In the book all these questions are probably answered. However, due to time constraint, the movie just can't cover all of it. Frankly a complex story like The Big Sleep doesn't fit the big screen too well.