1
general::
Phrase(s): *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.
McGrawhill's American Idioms And Phrasal Verbs