Nathan Fillion loses a smoking gun in The Rookie season finale sneak peek

It looks like John Nolan just made a rookie mistake.

Nolan (Nathan Fillion) has been put to the test throughout season 2 of The Rookie, facing off against serial killers and even doing some brief undercover work. But just as his first year on the force is coming to an end, he might be facing his toughest challenges yet. In this exclusive clip above from the first installment of the two-part season finale, Nolan misplaces a crucial piece of evidence: the gun used in an officer-involved shooting.

After returning from riding with his mentor Det. Nick Armstrong (Harold Perrineau), Nolan goes to book the evidence, but he's disturbed to find the gun is missing from his lockbox. He searches the station, retraces his steps, and double-checks the police car, but the gun nowhere to be found. So he goes to face Sergeant Grey (Richard T. Jones) and tell him the bad news.

Part 1 of the finale, "The Q Word," will find officers Nolan, Chen, and West preparing for their training officers to evaluate their preparedness to graduate from rookie status. But after one of their classmates is involved in a shooting, the team uncovers some unsettling evidence. Might it be tied to the missing weapon?

Watch the video above for more. "The Q Word" airs Sunday, May 3, at 10 p.m. ET/PT on ABC. Part 2, "The Hunt," will air May 10.

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