I think this because there is a murder scene, meaning that the film is going to involve a murderer, and I think that it is safe to presume that the detectives" main purpose will be to solve the murders, and catch the killer. .
Straight away in "Se7en", it is made apparent that there is a contrast between the two main characters, Detective Mills and Lieutenant Somerset. This clash of personalities is displayed when the two detectives are shown getting ready in the morning. Lieutenant Somerset is a very clean, organised person, who knows exactly what he is doing. He lives by himself in a bad neighbourhood, which may suggest that his life is unfulfilled. Detective Mills, however, is displayed as messy and disorganised, and he is not alone, as he lives with his wife. In my opinion, David Fincher - the director, is trying to show the audience that the two detectives are complete opposites, and this suggests that they are not going to get along. The fact that they do not get along implies that there may be great rivalries between the two police officers, as well as the murderer. This goes along with the genre of the film, as there will be many unpleasant scenes involving violence, and few friendships within the storyline. This contrast is also shown when the two men are together, as they do not seem to agree, "you know, it would be better for me if we didn't start out kicking each other in the balls", and in my opinion, Lieutenant Somerset is seen as in control. I have come to this conclusion because he seems very calm, and has authority over Detective Mills. Also, when they are walking down the street, people seem to be walking into Mills, and avoiding Somerset. This is just a simple observation, but I believe that it helps to signify the difference between the two characters. Lieutenant Somerset is also seen as a very considerate man, as he seems to care very much for his work and maybe gets a little too attached, "Did the kids see?".