"Only a police spy would talk politics to a stranger," he said grimly.

This led to many later claims that he was a police spy.

They were suspicious of him, at first; newcomers could always be possible police spies or informants.

I suspect that they have been penetrated by an undercover police spy.

They decided he must be a police spy and pounced on him.

Either she thinks we're police spies or she's made up her mind to rob us.

Doesn't this mean that our Presidents would be permanently surrounded by police spies?

It could lead to great things: every member of Congress surrounded by police spies, for example.

He'll put you on the spot as having taken part in the murder of that other police spy.