Hero: Main detective, a bit of an oddball, emotional wreck. Has chronic problems with their partner or love interest, bonus if they have a neglected child. Has a substance abuse problem or PTSD from a previous investigation which makes them not defer to authority. Everyone is against the hero because of their shortcomings until the very end where everyone realizes they've been wrong all along.
Sidekick: Doubts the hero but has irrational urge to be with them until they have a point of revelation where they start worshiping them. They tone down the edge of the hero by a notch and are a conduit to authority and the audience. Their happy personal life also suffers. Bonus: Always shot or maimed towards the end.
Victims: A young girl, SA for more shock value. Young boy for pedo angle, or a rich businessman or politician. It takes 10 homeless people before the police start to take notice so the equation goes: 10 homeless people = 1 young girl.
Villain: Usually seen within the first 20 minutes and the story tries hard to direct your attention away from them. Normal but perverse, definitely a serial killer selling pizza or something. Comes in the penultimate scenes to shoot the sidekick. Likes to commit suicide. Otherwise they're the victim of their circumstances (war, bad upbringing, corruption around them) but they start a chain reaction of rampage they cannot control.
Head of Police: Dumbest of the lot, makes you wonder why they're the head of police to begin with. Have no head, no spine, a bag of jelly to shut down the hero at convenient points. If a politician is the victim then the head of police is covert corrupt.
Hero's love interest: Usually a nice person but they're sick of the hero's chronic lateness and lack of romance. Bonus: thinks the hero is cheating on them. The middle episodes are devoted to their fucked up love life.
Victim's family: Broken, if it's a girl they're double broken. Seen gazing at the photos of the victim and banging their chest in front of police. At some point the male character lashes out at a potential perpetrator. They're humans made of glycerin.
Other characters: Seen giving support to victims or the Hero, the killer usually hiding in this lot. There's a funny one here for the laughs, one of them is dispensable, usually the villain gets them. All of them are are potential suspects and all of them are interrogated by the police which turns the community against them. Most of them have served jailtime, were corrupt or have cheated on their partners.
Pre-climax: Everyone zeroes on an Ersatz villain and the Head of Police insists an arrest be made. An arrest is made but the Hero can't sleep, they go rogue infuriating the Head of Police who already have the Hero suspended. Only the Sidekick realizes their brilliance and goes co-rogue usually without the knowledge of the Hero.
Climax: Sidekick is shot, Hero's blood is pumping napalm and goes full ballistic. Goes after the villain alone even as Head of Police is waiting at the wrong place with a battalion enough to invade Moscow (homage to Silence of the Lambs). Hero fights villain alone, killing them. (if not, suicide)
Last 15 minutes: Head of Police makes a joke of how stubborn the Hero is while toasting on the success of the investigation where they did jackshit. Hero is sleepless and mourns sidekick not being there (or they smile from the hospital bed). Montage of everyone healing, Fin.
Themes: If a politician is a victim then there's the obvious political cover-up and Hero always finds the killer but the victory ends on a bittersweet note with them being transferred or the real crime not exposed because corruption perpetuates over morality. If little children/young girls are involved the themes of human resilience, emotions and frailty are pondered upon. If homeless people are the victims then societal apathy is the theme of the show. Obviously the Hero is the white dove in a sea of sewage.