Spoiler warning: Spoilers for the complete film, including the police conspiracy.
Summer dies because she threatens to expose a property scheme involving the Gradys and corrupt police officers. Solving the case in Reptile forces Tom Nichols to investigate the people whose authority should have made the investigation possible.
How does the property scheme work?
Drugs are planted, properties are seized, and the Gradys profit from the real estate that changes hands. Summer’s attempt to contact the FBI threatens to connect those activities.
The reused, recognizably packaged heroin matters because it turns an apparently separate drug case into evidence of coordination. The investigation stops being a choice between isolated suspects and becomes a question about who controls the process.
Summer has reason to approach federal authorities: local officers are implicated. The apparent safety of reporting a crime disappears when the people receiving the report may benefit from keeping it hidden.
What does Tom discover about the people close to him?
The corruption reaches Wally, Captain Allen and Chief Graeber. A confrontation leaves Allen dead; Tom survives the clash with the other officers. Will is later arrested on the golf course.
Allen’s involvement makes the discovery personal as well as professional. Netflix’s cast guide identifies him as Tom’s mentor and Judy’s uncle. Reporting what Tom finds risks relationships that extend beyond the station.
Judy provides a different kind of partnership. The same guide describes how Tom relies on her judgment about cases. Where his colleagues’ familiarity conceals danger, the conversations at home offer him a way to test what he thinks he knows.
Does the ending identify Summer’s killer beyond doubt?
Will is deeply implicated, but the official explanation is cautious about his precise role in the physical killing. The clearer answer is why Summer had to be silenced and who benefited. Arrest and proof of every individual action are different things.
That distinction is worth preserving rather than replacing uncertainty with a neat name. The scheme depends on several people doing their part and trusting that nobody inside the network will speak.
Tom breaks that expectation. The ending makes his integrity costly: doing his job properly means refusing the protection of his own circle. Summer’s case exposes a system that could turn ordinary police procedure into a tool for taking someone else’s home.
Sources: official ending breakdown; additional reporting and explanation; additional context.