"When did you come to Lexington, Mr. Pym?"

The question proceeded from Mrs. Carleton, who had slipped into a seat beside him. He answered that he had arrived only that evening; had been sent for to see a patient.

"Who is it?" she asked.

"A young man suffering from heart disease," promptly responded Mr. Pym, deeming this positive evasion justifiable under the circumstances.

"And so you took the opportunity to call at Castle Wafer!" she said. And there might have been the slightest possible resentment perceptible in the tone, though not to an ear less quick than the surgeon's.

"Just so," he answered. "When we have nothing particular to do with ourselves, we are apt to make use of any past civilities that may be available. I remembered that Mr. Frederick St. John, when I met him at Alnwick, proffered me an invitation to call at Castle Wafer, should I ever travel to its vicinity."

"Oh!" she said. "Fred St. John's rather fond of those impromptu invitations. Do you go back tomorrow?"

"Not unless my patient shall have done with me."

Mr. Pym remained at Castle Wafer, a temporary guest. In the most natural manner conceivable, Frederick St. John, without being suspected of any ulterior motive, pressed the invitation on the little surgeon. Castle Wafer would be a more comfortable roof for him than the Barley Mow, and his sojourn there would afford him, Frederick, an opportunity of improving the acquaintance begun at Alnwick, he graciously observed, when they had met at the funeral of Mr. Carleton St. John. Mr. Pym suffered himself to be persuaded. And thus the surgeon took up his task of watching Mrs. Carleton, a very private-detective; installed thereunto by two anxious parties, neither of whom suspected the connivance of the other. What wheels within wheels there are in this world!

In one sense of the word, the step might have been dispensed with, for it did not serve to prevent the disclosure to Sir Isaac St. John. Mrs. Darling's great hope from the respite of the two or three days' watching, was, that she should in the meanwhile succeed in inducing Charlotte to bid adieu to Castle Wafer, and thus obviate the necessity for any appeal to Sir Isaac. It might have proved so, so far as Mr. Pym was concerned; but the initiative was taken by the dean.