on the trail

on the trail of (someone or something)

Following, pursuing, or tracking someone or something. Police are on the trail of two armed men who held up a liquor store late last night. Our top detective is on the trail of the stolen goods, sir.
See also: of, on, trail
Farlex Dictionary of Idioms.

*on the trail (of someone or something)

 and *on the track of someone or something
seeking someone or something; about to find someone or something. (*Typically: be ~; get ~.) I'm on the trail of a new can opener that is supposed to be easier to use. I spent all morning on the track of a vendor who can meet our requirements.
See also: on, trail
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • on the trail of (someone or something)
  • on the track of (someone or something)
  • hot on the trail
  • hot on the trail of (someone or something)
  • hot on the track of (someone or something)
  • leeky store
  • punk out
  • candy store
  • tongue oil
  • hooched up
References in classic literature
In the summer-time Indians might be met with at the mouths of the Stewart and White rivers, at the Big and Little Salmons, and on Lake Le Barge; but in the winter, as he well knew, they would be on the trail of the moose-herds, following them back into the mountains.
Burning Daylight
Maybe she make fun, too, so I say, 'Let me see thousand dollars.' And that woman, that young woman, all alone on the trail, there in the snow, she take out one thousand dollars, in greenbacks, and she put them in my hand.
There are few people on the trail. Sometimes we travel one hundred miles and never see a sign of life.
I was born on the trail, and all my days have I lived on the trail.
Standing or kneeling, always do they fall forward, gaining on the trail each time by the length of their bodies.
Love of Life And Other Stories