Film Idea

My film would be a murder mystery where the chief of police would be murdered at the begging of the film and the rest of the film would be about finding out who did it and it will take the characters on a physical and psychological journey. From the moment the murder happens the wife of the police chief starts to gets mysterious texts from a random number and is harassed by the potential murderer asking for money in return for he safety. It will be up to the police to out who this is and who committed the murder, the police in charge of the investigation would be the DCI and DI and they would try and find out who killed the police chief. They would go to a series of locations to try and find clues which would lead them to different suspect and would get close to prosecuting a lead but then they will find new evidence that says it is someone else until eventually they are confronted by the murderer face to face. who could to be? The characters will have their own suspicions as to who it was and will eventually put all the evidence together to find that it was the DI who did it because his brother was murdered and the police chief was in charge of the investigation and they did nothing  to try and find who did it so in revenge the DI took the police chiefs life.