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

*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
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.
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.
I, too, go on and on, because I am strong on the trail and because I am greatly paid.
Yet ever are we hitting the trail in the dark before daylight, and still on the trail does the dark after nightfall find us.
Time was flying, and they should have been on the trail an hour gone.
Dave refused to run quietly on the trail behind the sled, where the going was easy, but continued to flounder alongside in the soft snow, where the going was most difficult, till exhausted.
They swung out on the trail with remarkable lack of exertion, turned their heads uneasily, and stopped in surprise.