be on the scent

be on the scent (of someone or something)

To be pursuing a potential lead in an attempt to find someone or something. With this new evidence, the detective thinks he's finally on the scent of the kidnappers.
See also: on, scent, someone

be on the ˈscent (of somebody/something)

have information that will lead you to somebody/something: The police are on the scent of the criminals.
See also: on, scent