To smell a rat

Related to To smell a rat: To let the cat out of the bag
See under Smell.
to have a sense of something wrong, not clearly evident; to have reason for suspicion.

See also: Rat, Smell

References in periodicals archive ?
30pm KAT is quick to smell a rat tonight when a bloke called Carl White turns up at Bianca's house claiming to be an old friend of Derek's.
After all, they are used to working in the dark and muck and, above all, should be easily best placed to smell a rat now.