In Crispin: The Cross of Lead, who is at the White Stag tavern?

Through bribery, Crispin convinces the guide, whom the
widow arranged to take him to the town walls and safety, to lead him instead to the
White Stag where the conspirators are meeting. So, the conspirators are at the White
Stag. Crispin approaches them for help in arranging an escape for Bear, who is being
held elsewhere. The conspirators decline because the town is heavily guarded but offer
to escort Crispin to the town square.

Once there, Crispin
discovers John Aycliffe and convinces him at knife point to release Bear. Had Crispin
not gotten to the conspirators at the White Stag, he never would have encountered
Aycliffe and Bear would never have escaped. Of course, the escape leads them right into
another ambush or two, but that's for another question.