This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / The Shield
This series has so much nightmare fuel to offer, but one thing that stands out: Armadillo Quintero gets arrested. He's a known murderer and rapist. A 12-year-old girl, against the wishes of her family, tells the police that he killed some people. He's held for several hours, in which he finds one of the girl's hair clips which fell off in the interrogation room while they were interviewing her. After they're forced to release him for lack of evidence, the girl disappears...then reappears in a daze, with a dove tattooed on her face—something established earlier in the episode as the mark Quintero left on a girl that he had raped and brutalized.