sniff out

verb2

1. •
   To find (something) by using the sense of smell.

   • Because they have far more powerful noses than humans, dogs are ideal to sniff out drugs.
2. •
   (figurative) To detect (something hidden or invisible).

   • Luisa Rey plays the ditzy reporter on her best behavior to assure Fay Li she poses no threat. Only then might she be given a free enough rein to sniff out Sixsmith’s fellow dissidents. — 2004