Movie Idea Plot! PLZ. Read! I need opinions!!!!?

[KellyRM]

Do you think this is a good plot?

Here is the cast:
-Sam (Danny's love interest, Roy's sister)
-Danny (Sam's love interest)
-Johnny (Sam's best friend, agent in training)
-Roy (Sam’s brother)

When Phoenix, Arizona Police can't catch a serial killer. They request the help of a federal agency. 3 people are put on the case (Sam, Danny, and Johnny). Roy forces his way onto the case by convincing the case assigner, that he specializes in Serial Killers, and although Sam and Danny are better agents, they aren’t better with this subject. But here's the twist, the Roy IS the serial killer. (He really wants to get on the case so that he can shut the investigation down from the inside, and also to see what information they have on him so far.) While they are on the case, Roy tries to get Sam and Danny (leaders of the case) to drop the case. Sam refuses, so Roy takes action. He hires people to help him out, and scare them out of the case. Sam and Johnny are attacked on numerous occasions. (He doesn't bother with Danny, because he’s the one of the best agents in the agency, and it’d be too hard to beat him up.) Eventually Roy takes it into his own hands, and decides to kill Sam, but Sam ends up killing him instead.

Also, during the beginning, Danny flirts with Sam, and she shows no interest in him, but as the story progresses, and Danny shows that he really cares about her, she begins to fall in love and by the end of the story they fall in love.

I’m working on getting a patent, but I wanted to see if people thought it was a good idea first.

All comments are welcome. Any suggestions or ideas are welcome too. Also, if you think that something is stupid, or doesn’t work in my story, then those comments are welcome too.