And then Antony's sudden appearance! Here was a complication. And Antony suggesting that they should try the window! Why, the window was just what he wanted to avoid. No wonder he had seemed dazed at first.

Ah, and here at last was the explanation why they had gone the longest way round and yet run. It was Cayley's only chance of getting a start on Antony, of getting to the windows first, of working them open somehow before Antony caught him up. Even if that were impossible, he must get there first, just to make sure. Perhaps they were open. He must get away from Antony and see. And if they were shut, hopelessly shut, then he must have a moment to himself, a moment in which to think of some other plan, and avoid the ruin which seemed so suddenly to be threatening.

So he had run. But Antony had kept up with him. They had broken in the window together, and gone into the office. But Cayley was not done yet. There was the dressing-room window! But quietly, quietly. Antony mustn't hear.

And Antony didn't hear. Indeed, he had played up to Cayley splendidly. Not only had he called attention to the open window, but he had carefully explained to Cayley why Mark had chosen this particular window in preference to the office window. And Cayley had agreed that probably that was the reason. How he must have chuckled to himself! But he was still a little afraid. Afraid that Antony would examine the shrubbery. Why? Obviously because there was no trace of anyone having broken through the shrubbery. No doubt Cayley had provided the necessary traces since, and had helped the Inspector to find them. Had he even gone as far as footmarks in Mark's shoes? But the ground was very hard. Perhaps footmarks were not necessary. Antony smiled as he thought of the big Cayley trying to squeeze into the dapper little Mark's shoes. Cayley must have been glad that footmarks were not necessary.

No, the open window was enough; the open window and a broken twig or two. But quietly, quietly. Antony mustn't hear. And Antony had not heard.... But he had seen a shadow on the wall.

They were outside on the lawn again now, Bill and Antony, and Bill was listening open-mouthed to his friend's theory of yesterday's happenings. It fitted in, it explained things, but it did not get them any further. It only gave them another mystery to solve.

"What's that?" said Antony.

"Mark. Where's Mark? If he never went into the office at all, then where is he now?"

"I don't say that he never went into the office. In fact, he must have gone. Elsie heard him." He stopped and repeated slowly, "She heard him, at least she says she did. But if he was there, he came out again by the door."

"Well, but where does that lead you?"

"Where it led Mark. The pa.s.sage."

"Do you mean that he's been hiding there all the time?" Antony was silent until Bill had repeated his question, and then with an effort he came out of his thoughts and answered him.

"I don't know. But look here. Here is a possible explanation. I don't know if it is the right one--I don't know, Bill; I'm rather frightened. Frightened of what may have happened, of what may be going to happen. However, here is an explanation. See if you can find any fault with it."

With his legs stretched out and his hands deep in his pockets, he lay back on the garden-seat, looking up to the blue summer sky above him, and just as if he saw up there the events of yesterday being enacted over again, he described them slowly to Bill as they happened.

"We'll begin at the moment when Mark shoots Robert. Call it an accident; probably it was. Mark would say it was, anyhow. He is in a panic, naturally. But he doesn't lock the door and run away. For one thing, the key is on the outside of the door; for another, he is not quite such a fool as that. But he is in a horrible position. He is known to be on bad terms with his brother; he has just uttered some foolish threat to him, which may possibly have been overheard. What is he to do? He does the natural thing, the thing which Mark would always do in such circ.u.mstances. He consults Cayley, the invaluable, inevitable Cayley.

"Cayley is just outside, Cayley must have heard the shot, Cayley will tell him what to do. He opens the door just as Cayley is coming to see what is the matter. He explains rapidly. 'What's to be done, Cay? what's to be done? It was an accident. I swear it was an accident. He threatened me. He would have shot me if I hadn't. Think of something, quick!'

"Cayley has thought of something. 'Leave it to me,' he says. 'You clear out altogether. I shot him, if you like. I'll do all the explaining. Get away. Hide. n.o.body saw you go in. Into the pa.s.sage, quick. I'll come to you there as soon as I can.'

"Good Cayley. Faithful Cayley! Mark's courage comes back. Cayley will explain all right. Cayley will tell the servants that it was an accident. He will ring up the police. n.o.body will suspect Cayley-Cayley has no quarrel with Robert. And then Cayley will come into the pa.s.sage and tell him that it is all right, and Mark will go out by the other end, and saunter slowly back to the house. He will be told the news by one of the servants. Robert accidentally shot? Good Heavens!

"So, greatly rea.s.sured, Mark goes into the library. And Cayley goes to the door of the office.... and locks it. And then he bangs on the door and shouts, 'Let me in!'"

Antony was silent. Bill looked at him and shook his head.

"Yes, Tony, but that doesn't make sense. What's the point of Cayley behaving like that?"

Antony shrugged his shoulders without answering.

"And what has happened to Mark since?"

Antony shrugged his shoulders again.

"Well, the sooner we go into that pa.s.sage, the better," said Bill.

"You're ready to go?"

"Quite," said Bill, surprised.

"You're quite ready for what we may find?"

"You're being dashed mysterious, old boy."

"I know I am." He gave a little laugh, and went on, "Perhaps I'm being an a.s.s, just a melodramatic a.s.s. Well, I hope I am." He looked at his watch.

"It's safe, is it? They're still busy at the pond?"

"We'd better make certain. Could you be a sleuthhound, Bill-one of those that travel on their stomachs very noiselessly? I mean, could you get near enough to the pond to make sure that Cayley is still there, without letting him see you?"

"Rather!" He got up eagerly. "You wait."

Antony's head shot up suddenly. "Why, that was what Mark said," he cried.

"Mark?"

"Yes. What Elsie heard him say."

"Oh, that."

"Yes I suppose she couldn't have made a mistake, Bill? She did hear him?"

"She couldn't have mistaken his voice, if that's what you mean."

"Oh?"

"Mark had an extraordinary characteristic voice."

"Oh!"

"Rather high-pitched, you know, and well, one can't explain, but-"

"Yes?"

"Well, rather like this, you know, or even more so if anything." He rattled these words off in Mark's rather monotonous, high-pitched voice, and then laughed, and added in his natural voice, "I say, that was really rather good."

Antony nodded quickly. "That was like it?" he said.

"Exactly."

"Yes." He got up and squeezed Bill's arm. "Well just go and see about Cayley, and then we'll get moving. I shall be in the library."

"Right."

Bill nodded and walked off in the direction of the pond. This was glorious fun; this was life. The immediate programme could hardly be bettered. First of all he was going to stalk Cayley. There was a little copse above the level of the pond, and about a hundred yards away from it. He would come into this from the back, creep cautiously through it, taking care that no twigs cracked, and then, drawing himself on his stomach to the edge, peer down upon the scene below him. People were always doing that sort of thing in books, and he had been filled with a hopeless envy of them; well, now he was actually going to do it himself. What fun!