Mr. Longvale’s two patients were removed to hospital that night, and, with a favourable report on the man’s condition from the doctors, Michael felt that one aspect of the mystery was a mystery no longer.

His old schoolmaster received a visit that night.

“More study?” he asked good-humouredly when Michael was announced.

“Curiously enough, you’re right, sir,” said Michael, “though I doubt very much whether you can assist me. I’m looking for an old history of Chichester.”

“I have one published in 1600. You’re the second man in the last fortnight who wanted to see it.”

“Who was the other?” asked Michael quickly.

“A man named Foss⁠—” began Mr. Scott, and Michael nodded as though he had known the identity of the seeker after knowledge. “He wanted to know about caves. I’ve never heard there were any local caves of any celebrity. Now, if this were Cheddar, I should be able to give you quite a lot of information. I am an authority on the Cheddar caves.”

He showed Michael into the library, and taking down an ancient volume, laid it on the library table.

“After Foss had gone I looked up the reference. I find it occurs only on one page⁠—385. It deals with the disappearance of a troop of horsemen under Sir John Dudley, Earl of Newport, in some local trouble in the days of Stephen. Here is the passage.” He pointed.

Michael read, in the old-fashioned type:

“The noble Earl, deciding to await hi∫ arrival, carried two companie∫ of hor∫e by night into the great caves which exi∫ted in the∫e times. By the merciful di∫pen∫ation of God, in Who∫e Hands we are, there occurred, at eight o’clock in the forenoon, a great land∫lide which entombed and de∫troyed all the∫e knights and ∫quires, and ∫ir John Dudley, Earl of Newport, ∫o that they were never more ∫een. And the place of this happening is nine miles in a line from this ∫ame city, called by the Romans Regnum, or Ciffancea∫ter in the ∫axon fa∫hion.”

“Have the caves ever been located?”

Mr. Scott shook his head.

“There are local rumours that they were used a century and a half ago by brandy smugglers, but then you find those traditions local to every district.”

Michael took a local map of Chichester from his pocket, measured off nine miles, and with a pair of compasses encircled the city. He noted that the line passed either through or near Sir Gregory’s estate.

“There are two Griff Towers?” he suddenly said, examining the map.

“Yes, there is another besides Penne’s place, which is named after a famous local landmark⁠—the real Griffin Tower (as it was originally called). I have an idea it stands either within or about Penne’s property⁠—a very old, circular tower, about twenty feet high, and anything up to two thousand years old. I’m interested in antiquities, and I have made a very careful inspection of the place. The lower part of the wall is undoubtedly Roman work⁠—the Romans had a big encampment here; in fact, Regnum was one of their headquarters. There are all sorts of explanations for the tower. Probably it was a keep or blockhouse. The idea I have is that the original Roman tower was not more than a few feet high and was not designed for defence at all. Successive ages added to its height, without exactly knowing why.”

Michael chuckled.

“Now if my theory is correct, I shall hear more about this Roman castle before the night is out,” he said.

He gathered his trunks from the hotel and took them off to his new home. He found that the dinner-table was laid for three.

“Expecting company?” asked Michael, watching Jack Knebworth putting the finishing touches on the table⁠—he had a bachelor’s finicking sense of neatness, which consists of placing everything at equal distance from everything else.

“Yuh! Friend of yours.”

“Of mine?”

Jack nodded.

“I’ve asked young Leamington to come up. And when I see a man of your age turning pink at the mention of a girl’s name, I feel sorry for him. She’s coming partly on business, partly for the pleasure of meeting me in a human atmosphere. She didn’t do so well today as I wanted, but I guess we were all a little short of our best.”

She came soon after, and there was something about her that was very sweet and appealing; something that went straight to Michael’s heart and consolidated the position she had taken there.

“I was thinking as I came along,” she said, as Jack Knebworth helped her off with her coat, “how very unreal everything is⁠—I never dreamt I should be your guest to dinner, Mr. Knebworth.”

“And I never dreamt you’d be worthy of such a distinction,” growled Jack. “And in five years’ time you’ll be saying, ‘Why on earth did I make such a fuss about being asked to a skimpy meal by that punk director Knebworth?’ ”

He put his hand on her shoulder and led her into the room, and then for the first time she saw Michael, and that young man had a momentary sense of dismay when he saw her face drop. It was only for a second, and, as if reading his thoughts, she explained her sudden change of mien.

“I thought we were going to talk nothing but pictures and pictures!” she said.

“So you shall,” said Michael. “I’m the best listener on earth, and the first person to mention murder will be thrown out of the window.”

“Then I’ll prepare for the flight!” she said good-humouredly. “For I’m going to talk murder and mystery⁠—later!”

Under the expanding influence of a sympathetic environment the girl took on a new aspect, and all that Michael had suspected in her was amply proven. The shyness, the almost frigid reserve, melted in the company of two men, one of whom she guessed was fond of her, while the other⁠—well, Michael was at least a friend.

“I have been doing detective work this afternoon,” she said, after the coffee had been served, “and I’ve made amazing discoveries,” she added solemnly. “It started by my trying to track the motorcar, which I guessed must have come into my street through a lane which runs across the far end. It is the only motorcar track I’ve found, and I don’t think there is any doubt it was my white-handed man who drove it. You see, I noticed the back tyre, which had a sort of diamond-shaped design on it, and it was fairly easy to follow the marks. Halfway up the lane I found a place where there was oil in the middle of the road, and where the car must have stood for some time, and there⁠—I found this!”

She opened her little handbag and took out a small, dark-green bottle. It bore no label and was unstoppered. Michael took it from her hand, examined it curiously and smelt. There was a distinctive odour, pungent and not unpleasing.

“Do you recognize it?” she asked.

He shook his head.

“Let me try.” Jack Knebworth took the bottle from Michael’s hand and sniffed. “Butyl chloride,” he said quickly, and the girl nodded.

“I thought it was that. Father was a pharmaceutical chemist, and once, when I was playing in his dispensary, I found a cupboard open and took down a pretty bottle and opened it. I don’t know what would have happened to me, only daddy saw me. I was quite a child at the time, and I’ve always remembered that scent.”

“Butyl chloride?” Michael frowned.

“It’s known as the ‘death drop’ or the ‘knockout drop,’ ” said Knebworth, “and it’s a drug very much in favour with sharks who make a business of robbing sailors. A few drops of that in a glass of wine and you’re out!”

Michael took the bottle again. It was a commonplace bottle such as is used for the dispensation of poisons, and in fact the word “Poison” was blown into the glass.

“There is no trace of a label,” he said.

“And really there is no connection with the mysterious car,” admitted the girl. “My surmise is merely guesswork⁠—putting one sinister thing to another.”

“Where was it?”

“In a ditch, which is very deep there and is flooded just now, but the bottle didn’t roll down so far as the water. That is discovery number one. Here is number two.”

From her bag she took a curious-shaped piece of steel, both ends of which had the marks of a break.

“Do you know what that is?” she asked.

“It beats me,” said Jack, and handed the find to Michael.

“I know what it is, because I’ve seen it at the studio,” said the girl, “and you know too, don’t you, Mr. Brixan?”

Mike nodded.

“It’s the central link of a handcuff,” he said, “the link that has the swivel.”

It was covered with spots of rust, which had been cleaned off⁠—by the girl, as she told him.

“Those are my two finds. I am not going to offer you my conclusions, because I have none!”

“They may not have been thrown from the car at all,” said Michael, “but, as you say, there is a possibility that the owner of the car chose that peculiarly deserted spot to rid himself of two articles which he could not afford to have on the premises. It would have been safer to throw them into the sea, but this, I suppose, was the easier, and, to him, the safer method. I will keep these.”

He wrapped them in paper, put them away in his pocket, and the conversation drifted back to picture-taking, and, as he had anticipated:

“We’re shooting at Griff Tower tomorrow⁠—the real tower,” said Jack Knebworth. “It is one of the landmarks⁠—what is there amusing in Griff Tower?” he demanded.

“Nothing particularly amusing, except that you have fulfilled a prediction of mine,” said Michael. “I knew I should hear of that darned old tower!”