He stooped and picked up a broken twig.

“It is still sappy. There are several. One quite close to the studio wall, and there’s another across the lane. If it should happen they were snapped off by the top of a vehicle, it must have moved from one side to the other. It is a fair chance, isn’t it, that they were broken by our van, and, if this is so, they give an idea of its height. Right?”

“That’s right, sir,” said Mr. Sligo, breathing loudly through his nostrils.

“You know all this sort of stuff, of course,” said Alleyn, “but it’s a characteristic example of outside work. Now come along to the garage.”

They walked along the lane through a wide entrance into the garage yard. Alleyn unlocked the garage doors and broke the police tape. It had begun to rain steadily.

“I took some measurements here last night, but it would be as well to verify them. Suppose you have a stab at it, Sligo.”

Sligo, intensely gratified, measured the width of the tyres and the wheel-base.

“The tyres are the same, sir. Look here, sir, here’s the patch on the rear tyre on the driving side. We found the trace on the left-hand as you faced the window, sir, so she was backed all right.”

“Good,” said Alleyn. “That’s the way, Sligo. Now take a look at the doorstep. Wait a moment. I’ll just have a go at the handle for prints.”

He opened his bag and got out his insufflator. The grey powder showed no prints on the door or doorknob. Alleyn closely examined the three steps, which were worn and dirty.

“Don’t touch these,” he said, and opened the door.

“Now then, Sligo— ”

“There they are, sir, there they are. Same marks on the top step. That’s the marks of them little wheels, sir, isn’t it?”

“I think so. Check them to make sure. Here are the measurements of the scars on the window-sill.”

Out came Sligo’s tape again.

“It’s them, for sure,” he said.

“Now have a look on the roof. If you climb on that bench, you’ll do no harm. Co carefully, though. You never know if you won’t spoil a perfectly good bit of evidence in the most unlikely spot.”

Sligo mounted the bench like a mammoth Agag, and peered over the roof of the caravan.

“Eh, there’s a-plenty of scratches, sir, right enough, and Gor’, Mr. Alleyn, there’s a bit of a twig jammed between the top roofing and the frame. Dug into the crack. Gor’, that’s a bit of all right, isn’t it, sir?”

“It is indeed. Can you reach it?”

“Yes, sir.”

“Take these tweezers and draw it out carefully. That’s right. Now you can come down. Let’s have an envelope, Fox, may we? We’ll put your twig in there, Sligo, and label it. How far is it from here to London?”

“Twenty miles exactly, sir, to the end of the drive from Shepherd’s Bush,” answered Sligo promptly.

“Right!”

Alleyn packed his case and began with Fox and Sligo to examine the yard and the gateway into the lane.

“Here are the tracks clear enough in the lane,” said Fox. “We’ve got enough here and more to show this caravan was driven into the lane, backed up to the studio window and loaded up through the window. Who does the caravan belong to?”

“Miss Troy, I think,” said Alleyn.

“Is that so?” responded Fox, without any particular emphasis.

“We’ll find out presently. Seal the garage up again, will you, Fox? Blast this weather. We’d better have a look at Pilgrim’s car.”

Basil Pilgrim’s car was a very smart supercharged two-seater. The upholstery smelt definitely of Valmai Seacliff, and one of the side-pockets contained an elaborate set of cosmetics. “For running repairs,” grunted Alleyn. They opened the dicky and found a man’s rather shabby raincoat. Pilgrim’s. “Also for running repairs, I should think.” Alleyn examined it carefully, and sniffed at it. “Very powerful scent that young woman uses. I fancy, Fox, that this is the pure young man’s garment for changing wheels and delving in engines. Now then, Sligo, you have a look at this. It’s ideal for demonstration purposes — the sort of thing Holmes and Thorndyke read like a book. Do you know Holmes and Thorndyke? You should. How about giving me a running commentary on an old raincoat?”

Sligo, breathing noisily, took the coat in his enormous hands.

“Go on,” said Alleyn; “you’re a Yard man, and I’m taking notes for you.”

“It’s a man’s mackintosh,” began Sligo. “Made by Burberry. Marked ‘B. Pilgrim’ inside collar. It’s mucked up like and stained. Inside of collar a bit greasy, and it’s got white marks, too, on it. Grease on one sleeve. That’s car grease, I reckon, and there’s marks down front. Pockets. Righthand: A pair of old gloves used, likely, for changing tyres. There’s other marks, too. Reckon he’s done something to battery some time.”

“Well done,” said Alleyn. “Go on.”

Sligo turned the gloves inside out.

“Left hand inside has got small dark stain on edge of palm under base of little finger. Left-hand pocket: Piece of greasy rag. Box of matches.” Sligo turned the coat over and over. “I can’t see nothing more, sir, except a bit of a hole in right-hand cuff. Burnt by cigarette, likely. That’s all, sir.”

Alleyn shut his note-book.

“That’s the method,” he said. “But—” He glanced at his watch. “Good Lord, it is eight o’clock. You’d better cut back to the studio or your relief will be giving you a bad mark.”

“Thank you very much, sir. I’m much obliged, sir. It’s been a fair treat.”

“That’s all right. Away you go.”

Sligo pounded off.

Leaving Fox at the garage, Alleyn walked round the house and rang the front-door bell. It was answered by a constable.

“Good morning. Do you know if Miss Troy is down yet?”

“She’s in the library, sir.”

“Ask if I may see her for a moment.”

The man came back to say Troy would receive Alleyn, and he went into the library. By daylight it was a pleasant room, and already a fire blazed in the open grate. Troy, in slacks and a pullover, looked so much as she did on that first morning at Suva that Alleyn felt for a moment as if there had been nothing between them but the first little shock of meeting. Then he saw that she looked as if she had not slept.

“You are early at your job,” said Troy.

“I’m very sorry, indeed, to worry you at the crack of dawn. I want to ask you if the caravan in the garage belongs to you.”

“Yes. Why?”

“When did you last use it, please?”

“About a fortnight ago. We all went out in it to Kattswood for a picnic and a day’s sketching.”

“Do you know how much petrol there was in the tank when you got back?”

“It must have been more than half full, I should think. I got it filled up when we started, and we only went about forty miles there and back.”

“What does she do to the gallon?”

“Twenty.”

“And the tank holds—?”

“Eight gallons.”

“Yes. It’s just over a quarter full this morning.”

Troy stared at him.

“There must be a leak in the petrol tank,” she said. “I couldn’t have used more than five that day — not possibly.”

“There isn’t a leak,” said Alleyn. “I looked.”

“Look here, what is all this?”

“You’re sure no one else has used the caravan?”

“Of course I am. Not with my permission.” Troy seemed puzzled and worried. Then as her eyes widened “Garcia!” she cried out. “You think Garcia took it, don’t you?”

“What makes you so sure of that?”

“Why, because I’ve puzzled my own wits half the night to think how he got his stuff away. The superintendent here told me none of the local carriers knew anything about it. Of course Garcia took it! Just like him. Trust him not to pay a carrier if he could get his stuff there free.”

“Can he drive?”

“I really don’t know. I shouldn’t have thought so, certainly. I suppose he must be able to drive if he took the caravan.” She paused and looked steadily at Alleyn.

“I know you think he went in the caravan,” she said.