He found Bill in the hall and proposed a stroll. Bill was only too ready. "Where do you want to go?" he asked.

"I don't mind much. Show me the park."

"Righto."

They walked out together.

"Watson, old man," said Antony, as soon as they were away from the house, "you really mustn't talk so loudly indoors. There was a gentleman outside, just behind you, all the time."

"Oh, I say," said Bill, going pink. "I'm awfully sorry. So that's why you were talking such rot."

"Partly, yes. And partly because I do feel rather bright this morning. We're going to have a busy day."

"Are we really? What are we going to do?"

"They're going to drag the pond-beg its pardon, the lake. Where is the lake?"

"We're on the way to it now, if you'd like to see it."

"We may as well look at it. Do you haunt the lake much in the ordinary way?"

"Oh, no, rather not. There's nothing to do there."

"You can't bathe?"

"Well, I shouldn't care to. Too dirty."

"I see.... This is the way we came yesterday, isn't it? The way to the village?"

"Yes. We go off a bit to the right directly. What are they dragging it for?"

"Mark."

"Oh, rot," said Bill uneasily. He was silent for a little, and then, forgetting his uncomfortable thoughts in his sudden remembrance of the exciting times they were having, said eagerly, "I say, when are we going to look for that pa.s.sage?"

"We can't do very much while Cayley's in the house."

"What about this afternoon when they're dragging the pond? He's sure to be there."

Antony shook his head.

"There's something I must do this afternoon," he said. "Of course we might have time for both."

"Has Cayley got to be out of the house for the other thing too?"

"Well, I think he ought to be."

"I say, is it anything rather exciting?"

"I don't know. It might be rather interesting. I daresay I could do it at some other time, but I rather fancy it at three o'clock, somehow. I've been specially keeping it back for then."

"I say, what fun! You do want me, don't you?"

"Of course I do. Only, Bill don't talk about things inside the house, unless I begin. There's a good Watson."

"I won't. I swear I won't."

They had come to the pond-Mark's lake-and they walked silently round it. When they had made the circle, Antony sat down on the gra.s.s, and relit his pipe. Bill followed his example.

"Well, Mark isn't there," said Antony.

"No," said Bill. "At least, I don't quite see why you know he isn't."

"It isn't 'knowing,' it's 'guessing,'" said Antony rapidly. "It's much easier to shoot yourself than to drown yourself, and if Mark had wanted to shoot himself in the water, with some idea of not letting the body be found, he'd have put big stones in his pockets, and the only big stones are near the water's edge, and they would have left marks, and they haven't, and therefore he didn't, and oh, bother the pond; that can wait till this afternoon. Bill, where does the secret pa.s.sage begin?"

"Well, that's what we've got to find out, isn't it?"

"Yes. You see, my idea is this."

He explained his reasons for thinking that the secret of the pa.s.sage was concerned in some way with the secret of Robert's death, and went on:

"My theory is that Mark discovered the pa.s.sage about a year ago--the time when he began to get keen on croquet. The pa.s.sage came out into the floor of the shed, and probably it was Cayley's idea to put a croquet-box over the trap-door, so as to hide it more completely. You know, when once you've discovered a secret yourself, it always seems as if it must be so obvious to everybody else. I can imagine that Mark loved having this little secret all to himself and to Cayley, of course, but Cayley wouldn't count and they must have had great fun fixing it up, and making it more difficult for other people to find out. Well then, when Miss Norris was going to dress-up, Cayley gave it away. Probably he told her that she could never get down to the bowling-green without being discovered, and then perhaps showed that he knew there was one way in which she could do it, and she wormed the secret out of him somehow."

"But this was two or three days before Robert turned up."

"Exactly. I am not suggesting that there was anything sinister about the pa.s.sage in the first place. It was just a little private bit of romance and adventure for Mark, three days ago. He didn't even know that Robert was coming. But somehow the pa.s.sage has been used since, in connection with Robert. Perhaps Mark escaped that way; perhaps he's hiding there now. And if so, then the only person who could give him away was Miss Norris. And she of course would only do it innocently not knowing that the pa.s.sage had anything to do with it."

"So it was safer to have her out of the way?"

"Yes."

"But, look here, Tony, why do you want to bother about this end of it? We can always get in at the bowling-green end."

"I know, but if we do that we shall have to do it openly. It will mean breaking open the box, and letting Cayley know that we've done it. You see, Bill, if we don't find anything out for ourselves in the next day or two, we've got to tell the police what we have found out, and then they can explore the pa.s.sage for themselves. But I don't want to do that yet."

"Rather not.

"So we've got to carry on secretly for a bit. It's the only way." He smiled and added, "And it's much more fun."

"Rather!" Bill chuckled to himself.

"Very well. Where does the secret pa.s.sage begin?"

CHAPTER XI. The Reverend Theodore Ussher