He had an idea that he knew who the boy was, but as yet could not be sure.

"I'll cut along to the public-house where this man was arrested," said Jennings, "I suppose you'll hold an inquest." "Certainly, seeing the man has been poisoned." Then the inspector proceeded to rebuke the constable who had performed his duty so ill, and threatened him with dismissal.

Jennings left in the midst of the trouble, after getting the inspector to promise that, he would report the result of the inquest.
At the public-house--it was the "White Horse," Keighley, an adjoining suburb--Jennings learned that the man who called himself--or rather who was called by his presumed son--Tyke, was not an habitue of the place.
Therefore, the boy could not have known that his supposed father was there.

Apparently some information had reached the lad, whereby he was able to trace Tyke to the prison, and had carried to him there the bottle of poisoned whisky.

Jennings returned to town quite satisfied that he had another clue to the existence of the coiners.