By this time we had reached the bottom of the garden.  Opening the gate, we followed the tracks towards the outhouse, which stood beside a cart-track; but as we came round the corner we both stopped short and looked at one another.  On the soft earth were the very distinct impressions of the tyres of a motor-car leading from the wide door of the outhouse.  Finding that the door was unfastened, Thorndyke opened it, and looked in, to satisfy himself that the place was empty.  Then he fell to studying the tracks.

“The course of events is pretty plain,” he observed.  “First the fellow brought down his luggage, started the engine, and got the car out—­you can see where it stood, both by the little pool of oil, and by the widening and blurring of the wheel-tracks from the vibration of the free engine; then he went back and fetched the boy—­carried him pick-a-back, I should say, judging by the depth of the toe-marks in the last set of footprints.  That was a tactical mistake.  He should have taken the boy straight into the shed.”

He pointed as he spoke to one of the footprints beside the wheel-tracks, from the toe of which projected a small segment of the print of a little rubber heel.

We now made our way back to the house, where we found Willett pensively rapping at the front door with a cycle-spanner.  Thorndyke took a last glance, with his hand in his pocket, at an open window above, and then, to the coachman’s intense delight, brought forth what looked uncommonly like a small bunch of skeleton keys.  One of these he inserted into the keyhole, and as he gave it a turn, the lock clicked, and the door stood open.

The little sitting-room, which we now entered, was furnished with the barest necessaries.  Its centre was occupied by an oilcloth-covered table, on which I observed with surprise a dismembered “Bee” clock (the works of which had been taken apart with a tin-opener that lay beside them) and a box-wood bird-call.  At these objects Thorndyke glanced and nodded, as though they fitted into some theory that he had formed; examined carefully the oilcloth around the litter of wheels and pinions, and then proceeded on a tour of inspection round the room, peering inquisitively into the kitchen and store-cupboard.

“Nothing very distinctive or personal here,” he remarked.  “Let us go upstairs.”

There were three bedrooms on the upper floor, of which two were evidently disused, though the windows were wide open.  The third bedroom showed manifest traces of occupation, though it was as bare as the others, for the water still stood in the wash-hand basin, and the bed was unmade.  To the latter Thorndyke advanced, and, having turned back the bedclothes, examined the interior attentively, especially at the foot and the pillow.  The latter was soiled—­not to say grimy—­though the rest of the bed-linen was quite clean.

“Hair-dye,” remarked Thorndyke, noting my glance at it; then he turned and looked out of the open window.  “Can you see the place where Miss Haldean was sitting to sketch?” he asked.