Outside at the taxi stand, the men approached and finally identified themselves: They turned out to be plain-clothes police.
I stopped at the station and brought along a couple of plain-clothes men, in case there was any trouble.
“There are half a dozen plain-clothes men in the audience,” he said.
It was signed by the chief of the Baltimore plain-clothes force.
The other two I guessed as plain-clothes men from Vancouver.
Please have plain-clothes men pick up Ellen in Washington Square.
"Well, yes, sir," admitted the plain-clothes man with reluctance.
If the plain-clothes man was willing to take the drink, all well and good, but if he refused--but he did not refuse.
He was the same man who had identified her to Spofford, the plain-clothes man.
Drive on, Lennard, until you can spot a plain-clothes man, then give him the signal to follow us.
"ordinary dress" (as opposed to military uniform), 1822; of police detectives, it is attested from 1842. Also plainclothes.