Meanwhile Humblethorne had been spending his time in the straightforward, though difficult, business of following up the stranger of the inn. Inquiry showed that he had left early on the morning after the crime, walked to the railway station and there caught the 8.7 a.m. train. He had taken no ticket, obviously having a return half. Having ascertained so much, first from Timmins and then by a visit to the station, Humblethorne walked back, intending to send off a long official telegram which would start the great machinery of the police force at work in picking up the trail. As he passed the post-office, however, an idea struck him; he sauntered in and over the sale of a picture postcard drifted easily into conversation with the postmaster on the great topic of the crime. A skilful suggestion about the awfulness of having to write such news to the son bore unexpected fruit; Miss Celia, it appeared, had written to him. The postmaster was easily drawn on to talk: the letter had attracted notice by being the first written to Mr. John since he was driven from home, think of that, and he had noticed the street and the suburb, though he couldn’t be certain of the number. The telegram that Humblethorne eventually dispatched in official code would do the rest. Humblethorne then devoted his energies to an endeavour to procure further identification, either of John Penterton or of Philip Castle from the cigarette box, but, as he had feared, the roughness of the surface, owing to the ornamentation and tooling, made the discovery of any finger-marks hopeless. Evelyn, had she thought of it further, only narrowly escaped falling under suspicion herself by virtue of this accident. One half of his inquiry, that relating to John, being now finished, Humblethorne next directed his attention to the finding of the evidence against Castle which he was firmly persuaded was still in existence. He walked up to the Towers, and, entering quietly, made his way up the back stairs. With unhurried, unwearied persistence he searched the two large unoccupied rooms, which were at the end of the passage past Castle’s room. He found no trace whatever of what he was looking for, entered John’s room and repeated the process, again without result. Puzzled, he stopped, wondering where he should search next. His glance fell upon the boots and it occurred to him that it would still further strengthen the chain of evidence if he verified his measurements: also he would re-examine the window in the hope that he might find he had overlooked some proof of the identity of the man who had bolted the shutters. He accordingly picked up the nearest boot of the row, went downstairs and crossed the hall into the drawing-room.