Decima seemed to hesitate.

“All right,” she said at last. She walked over to a rock at the edge of the track and sat on it. Alleyn and Fox followed her.

She looked at them with the kind of assurance that is given to women who are unusually lovely and sometimes to women who are emphatically plain. She was without self-consciousness. Nobody had told Alleyn that Decima was beautiful and he was a little surprised. “It’s impossible,” he thought, “that she can be in love with young Pomeroy.”

“I suppose it’s about Luke Watchman,” said Decima.

“Yes, it is. We’ve been sent down to see if we can tidy up a bit.”

“Does that mean they think it was murder?” asked Decima steadily. “Or don’t you answer that sort of question?”

“We don’t,” rejoined Alleyn smiling, “answer that sort of question.”

“I suppose not,” said Decima.

“We are trying,” continued Alleyn, “to trace Mr. Watchman’s movements from the time he got here until the time of the accident.”

“Why?”

“Part of the tidying-up process.”

“I see.”

“It’s all pretty plain sailing except for Friday morning.”

Alleyn saw her head turn so that for a second she looked towards Ottercombe Tunnel. It was only for a second, and she faced him again.

“He went out,” said Alleyn, “soon after breakfast. Mr. Pomeroy saw him enter the tunnel. That was about ten minutes before you left Ottercombe. Did you see Mr. Watchman on your way home?”

“Yes,” she said, “I saw him.”

“Where, please?”

“Just outside the top of the tunnel by some furze-bushes. I think he was asleep.”

“Did he wake as you passed him?”

She clasped her thin hands round her knees.

“Oh, yes,” she said.

“Did you stop, Miss Moore?”

“For a minute or two, yes.”

“Do you mind telling us what you talked about?”

“Nothing that could help you. We — we argued about theories.”

“Theories?”

“Oh, politics. We disagreed violently over politics. I’m a red rebel, as I suppose you’ve heard. It rather annoyed him. We only spoke for a moment.”

“I suppose it was apropos of the Coombe Left Movement?” murmured Alleyn.

“Do you?” asked Decima.

Alleyn looked apologetic. “I thought it might be,” he said, “because of your interest in the Movement. I mean it would have been a sort of natural ingredient of a political argument, wouldn’t it?”

“Would it?” asked Decima.

“You’re quite right to snub me,” said Alleyn ruefully. “I’m jumping to conclusions and that’s a very bad fault in our job. Isn’t it, Fox?”

“Shocking, sir,” said Fox. Alleyn pulled out his note-book. “I’ll just get this right if I may. You met Mr. Watchman at about what time?”

“Ten o’clock.”

“At ten o’clock or thereabouts. You met him by accident. You think he was asleep. You had a political argument in which the Coombe Left Movement was not mentioned.”

“I didn’t say so, you know.”

“Would you mind saying so or saying not so? Just for my notes?” asked Alleyn, with such a quaint air of diffidence that Decima suddenly smiled at him.

“All right,” she said, “we did argue about the society, though it’s nothing to do with the case.”

“If you knew the numbers of these books that I’ve filled with notes that have nothing whatever to do with the case you’d feel sorry for me,” said Alleyn.

“We’ll manage things better when we run the police,” said Decima.

“I hope so,” said Alleyn gravely. “Was your argument amicable?”

“Fairly,” said Decima.

“Did you mention Mr. Legge?”

Decima said: “Before we go any further there’s something I’d like to tell you.”

Alleyn looked up quickly. She was frowning. She stared out over the downs, her thin fingers were clasped together.

“You’d better leave Robert Legge alone,” said Decima. “If Watchman was murdered it wasn’t by Legge.”

“How do you know that, Miss Moore?”

“I watched him. He hadn’t a chance. The others will have told you that. Will, Norman Cubitt, Miss Darragh. We’ve compared notes. We’re all positive.”

“You don’t include Mr. Parish?”

“He’s a fool,” said Decima.

“And Mr. Abel Pomeroy?”

She blushed, unexpectedly and beautifully.

“Mr. Pomeroy’s not a fool but he’s violently prejudiced against Bob Legge. He’s a ferocious Tory. He thinks we — he thinks Will and I are too much under Bob’s influence. He hasn’t got a single reasonable argument against Bob, he simply would rather it was Bob than anyone else and has hypnotized himself into believing he’s right. It’s childishly obvious. Surely you must see that. He’s an example in elementary psychology.”

Alleyn raised an eyebrow. She glared at him.

“I’m not disputing it,” said Alleyn mildly.

“Well then—”

“The camp seems to be divided into pro-Leggites and anti-Leggites. The funny thing about the pro-Leggites is this: They protest his innocence and, I am sure, believe in it. You’d think they’d welcome our investigations. You’d think they’d say, ‘Come on then, look into his record, find out all you like about him. He’s a decent citizen and an innocent man. He’ll stand up to any amount of investigation.’ They don’t. They take the line of resenting the mildest form of question about Legge. Why’s that, do you suppose? Why do you warn us off Mr. Legge?”

“I don’t—”

“But you do,” insisted Alleyn gently.

Decima turned her head and stared searchingly at him.

“You don’t look a brute,” she said doubtfully.

“I’m glad of that.”

“I mean you don’t look a complete robot. I suppose, having once committed yourself to a machine, you have to tick-over in the appointed manner.”

“Always providing someone doesn’t throw a spanner in the works.”

“Look here,” said Decima. “Bob Legge had an appointment in Illington that evening. He was just going, he would have gone if Will hadn’t persuaded him not to. Will told him he’d be a fool to drive through the tunnel with the surface water pouring through it.”

She was watching Alleyn and she said quickly, “Ah! You didn’t know that?”

Alleyn said nothing.

“Ask Will. Ask the man he was to meet in Illington.”

“The local police have done that,” said Alleyn. “We won’t question the appointment. We only know Mr. Legge didn’t keep it.”

“He couldn’t. You can’t drive through that tunnel when there’s a stream of surface-water pouring down it.”

“I should hate to try,” Alleyn agreed. “We’re not making much of an outcry over Mr. Legge’s failure to appear. It was you, wasn’t it, who raised the question?”

“I was only going to point out that Bob didn’t know there would be a thunderstorm, did he?”

“Unless the pricking of his thumbs or something—”

“If this was murder I suppose it was premeditated. You won’t deny that?”

“No. I don’t deny that.”

“Well then! Suppose he was the murderer. He didn’t know it would rain. It would have looked pretty fishy for him to put off his appointment for no reason at all.”

“It would. I wonder why he didn’t tell me this himself.”

“Because he’s so worried that he’s at the end of his tether. Because you got hold of him last night and deliberately played on his nerves until he couldn’t think. Because—”

“Hullo!” said Alleyn. “You’ve seen him this morning, have you?”

If Decima was disconcerted she didn’t show it. She blazed at Alleyn.

“Yes, I’ve seen him and I scarcely recognized him. He’s a mass of overwrought nerves. His condition’s pathological. The next thing will be a confession of a crime he didn’t commit.”

“How about the crime he did commit?” asked Alleyn. “It would be more sensible.”

And that did shake her. She caught her breath in a little gasping sigh. Her fingers went to her lips. She looked very young and very guilty.

“So you knew all the time,” said Decima.