From Longman Dictionary of Contemporary Englishsmell a ratsmell a ratinformalSUSPECT to guess that something wrong or dishonest is happening → smell
Examples from the Corpus
smell a rat• She felt that he was beginning to smell a rat.• Suffice to say, we smell a rat.• It is enough to make you smell a rat and be damned for your cynicism.• He could smell a rat, and he knew just how the men had been cheated.• I smell a rat here - I really do.• The investor doesn't start to smell a rat until the payments aren't coming in.• I only began to smell a rat when he couldn't come up with the documents he claimed to have.• We started to smell a rat when they asked for an extra £500 deposit. 