Menace
A common theme found in the film-noir genre is that of menace, and this story is no exception. Throughout the picture we watch as Marlowe encounters Moose Malloy whose initial presence is a haunting image portrayed in the reflection of Marlowe's window as he towers over the private eye. Every scene that Malloy is in we feel the possibility that he could hurt someone. And this threat becomes real when we see his physical strength used against people to incite fear within them in order to get them to do what he wants. Then we have Amthor whose menace is a psychological one. He uses drugs in order to gain control over people and because he has gained a prominent place in business he pays people to do what he pleases. Thus, every time he is in a scene there is an underlying tension between he and the other characters because his threat is one that could come at any moment as his specialty is the mind, and cracking it open.
Who Done It
Another theme is "Who done it." Within this film the plot is based on a mystery that must be solved by our private investigator, Marlowe. Every film noir is about finding clues that lead to the next clue and eventually to the killer. This film not only has us searching for a killer, it throws us off the trail of who it could possibly be as it appears that nearly everyone is a suspect. This includes Marlowe as well, as we see him being pulled in by the police for questioning every time something happens. As the narrator of the film, Marlowe serves as our guide to cracking the case. And a common element in a noir style film is that we, the audience feel like we are the ones solving the mystery so, we then engage with the film in an interactive way in order to bring the criminal to justice.
Betrayal
Marlowe has set his sights on finding Marriott's killer and where the necklace is that got him into so much trouble. He does so because everyone that asks him for help has eventually attempted to pay him in order to stop investigating. As the picture becomes clearer we begin to understand that each relationship is not as simple as it appears. Amthor is using Moose Malloy as muscle to shake down Marlowe and Helen. Amthor pays with his life for betraying Malloy as he's told him that Velma has been with Marlowe which isn't true.
We then watch as Helen employs Marlowe to find Marriott's killer and she does so with the promise of being his lover and giving him all the money he needs. It turns out she is only using him to kill Amthor to get rid of any evidence that it was her that killed Marriott and knocked Marlowe out in the canyons. She not only betrays Marlowe, but her husband as well. She isn't satisfied with only having his money. She needed more encounters with men, and wasn't willing to give them up for him so she created a phony plot about her necklace being stolen in order to cause a break in their relationship so she could get more money. And Lastly, Mr. Grayle betrays his wife, Helen by killing her before she can pull the trigger on Marlowe. He can't go on like this anymore and his only answer is to end the relationship permanently.
