Smell a rat

Oh, Are you thereabouts, Sir; then I ſmell a Rat Ifaith; but I'll ſay nothing.

[O]ur conjectures were like arrows ſhot in the dark—they were wide of the mark—till an old gentleman came into the room, who after affixing his ſpectacles on the ſuperior part of an aquiline noſe, told us—"he ſmelt a rat!" / "He ſmelt a rat!" and ſhaking his head with all the ſolemnity of Attic ſagacity—whiſpered to the perſon next his elbow, / "I know it!"

Mr. Gresham, when he heard this, thought that he began to smell a rat, and was determined to be on his guard.

[John Broadus] Watson would have liked to continue his infant studies, but he never had the chance. His wife smelled a rat and found out his affair with his graduate student assistant, Rosalie Rayner.

“If I had told you my ideas, the very first time you saw Mr. Alfred Inglethorp that astute gentleman would have—in your so expressive idiom—‘smelt a rat’! And then, bonjour to our chances of catching him!”

Eventually, the job was re-advertised and she applied for it. She applied repeatedly over several years, but was never selected. She began smelling a rat (this being a land managing agency, a woodrat). She did some checking and found out that contrary to its promises, the agency had done all it could to "blackball" her from working in federal service again.

One anecdote holds that when a pro-Constitution opponent demanded to know why [Patrick] Henry had not attended the convention, he replied, "I smelt a rat." Henry scented that decaying rodent in the notion that the states should surrender more power to a new national government.

If Collins smells a rat, you might gain nothing and tempt the gang to persecute you and your daughter.

[Harold] Levin told us that he spent an hour with [Jeff] Epstein in his office and immediately got a bad vibe. He found a pay phone and called [Les] Wexner. “I smell a rat,” Levin reported. “I don’t trust him.”