Mrs. Pelgrin welcomed her unexpected guests with great delight and showed her appreciation of their coming by emphatic aggressiveness. Why she should mask a kind heart and an excellent disposition by assuming a brusque demeanour is not very clear, but certainly the more amiable she felt the more disagreeable did she become. In fact, the landlady appeared to believe that honesty of purpose was best shown by blunt speeches and abrupt movements. Consequently, she did not get on particularly well with Mrs. Bolstreath, who demanded respect and deference from underlings, which Mrs. Pelgrin positively declined to render. She termed the chaperon “a fine madam,” in the same spirit as she had called Dan “a butterfly,” and was always ready for a war of words. But, admiring Lillian’s gay and lively character, she waited on the girl hand and foot, yet with an air of protest to hide the real satisfaction she felt at having her in the house. To Mrs. Pelgrin, Lillian was a goddess who had descended from high Olympus to mingle for a time with mere mortals.

Out of consideration for Halliday’s desire to seek safety for Lillian by placing her under the guns of the enemy, Mrs. Bolstreath decided to remain a week at The Peacock Hotel. Later she arranged to go to Hartlepool in Durhamshire, where she and her charge could find shelter with two spinsters who kept a school. The chaperon admitted that she felt uneasy in the near vicinity of Queen Beelzebub, and all Dan’s assurance could not quieten her fears. She thought that he was playing too bold a game, and that ill would come of the stay at Sheepeak. Lillian was more confident, always confident that Dan could do no wrong, and she was quite indifferent to Mrs. Jarsell’s doings. However, she agreed to go to Hartlepool, and as Mrs. Bolstreath was bent upon the change, Halliday accepted the situation.

Meanwhile, he decided to call at The Grange on some innocent pretext and diplomatically give Queen Beelzebub to understand that he held the winning card in the game he was playing with the Society of Flies. This could be done, he ventured to think, by pretending that Mrs. Jarsell knew nothing about the nefarious association, and he did not believe that she would remove her mask, since it was to her interest to observe secrecy in Hillshire. However, he left this matter of a call and an explanation in abeyance for the time being, and for a couple of days attended to the three ladies. The third, it is needless to say, was Mildred Vincent, who called at The Peacock Hotel on receipt of her lover’s letter. She gave Dan to understand that he was out of favour with the inventor.

“Uncle has never forgiven you for not winning the race,” said Mildred, at afternoon tea; “he says you should have gained the prize.”

“I wish I had,” said Halliday, drily, “the money would have been very acceptable. It was my fancy-flying did the mischief, as I broke the rudder. However, I shall call and apologise.”

“He won’t see you, Mr. Halliday.”

“Ah, that’s so like an inventor, who is as touchy as a minor poet.”

“Mrs. Jarsell is annoyed also,” continued Mildred, sadly; “she says you should have made a better use of the favour she procured for you.”

“It seems to me that I am in hot water all round, Miss Vincent. All the same, I shall survive these dislikes.”

“It is absurd,” cried Lillian, with indignation. “Dan risked his life to win the race, and if he hadn’t had such bad luck he would have won.”

“Thanks, my dear girl, but it was less bad luck than carelessness, and a certain amount of vanity, to show how I could handle the machine.”

“You are very modest, Dan,” said Mrs. Bolstreath, laughing.

“It is my best quality,” replied Halliday, with a twinkle in his eyes.

“Where is Mr. Vincent’s machine now?” questioned Mildred.

“At Blackheath stored away. I suppose, as it was only lent I shall have to return it to your uncle. But I shall have a final fly on it when I go back to London in a few days.”

“Does Miss Moon go back also?”

“Not to London,” interposed Mrs. Bolstreath, “we propose to visit some friends in Scotland.”

Lillian looked up in surprise, as Hartlepool certainly was not in Scotland, and she thought that Mrs. Bolstreath’s geography was at fault. But a significant look from Dan showed her that he understood why the wrong address had been given. Mrs. Bolstreath, with too much zeal, mistrusted Mildred, although she had no cause to do so. Certainly Mildred, in perfect innocence, did she know the actual destination, might tell her uncle, who would assuredly tell Mrs. Jarsell, and for obvious reasons it was not necessary that Mrs. Jarsell should learn where the city of refuge was situated. All the same, Dan did not think for a moment that Mildred knew anything about the Society of Flies. But he was beginning to fancy that Vincent had some such knowledge, as Mrs. Jarsell financed him, and that she would not do so, he was positive, unless she made something out of the business. It was very convenient for Queen Beelzebub to have an inventor at her elbow who could construct swift aeroplanes. And it was at this point of his meditations that Dan jumped up so suddenly as to spill his tea.

“What’s the matter?” asked Lillian, making a dash at the cup and saucer to save breakage.

“I’ve got an idea,” said Halliday, with a gasp. “I must go out and think it over,” and without excusing himself further, he rushed from the room.

“That’s not like Dan,” remarked Mrs. Bolstreath, uneasily; “he is calm and cool-headed as a rule. I wonder what is the matter.”

“Oh, he’ll tell us when he comes back,” replied Lillian, philosophically. “I can always trust Dan.” Then she turned the conversation in a somewhat heedless manner. “Do you like living here, Miss Vincent?”

“Well,” admitted Mildred, “it is rather too quiet for my taste. But I have plenty to do in looking after my uncle and his business. He depends so much on me, that I wonder what he will do when I get married.”

“When do you intend to get married?” asked Mrs. Bolstreath, curiously. She could not disabuse herself of the idea that, living so close to Mrs. Jarsell, and having an uncle who was helped by Mrs. Jarsell, the girl knew something about the Society of Flies.

“Next year, the year after — I don’t exactly know. It all depends upon my dear Freddy’s success. We must have a home and an income. But I suppose we shall marry sooner or later, and then Mrs. Jarsell can look after Uncle Solomon.”

“Who is Mrs. Jarsell?” asked Lillian, artfully and cautiously.

“Se is an old lady who lives at The Grange with another old lady, her former governess, Miss Armour. Both are charming. If you are dull here, perhaps, Miss Moon, you would like to meet them?”

“Later, later,” put in Mrs. Bolstreath, hurriedly; “thank you for the suggestion, Miss Vincent. Meanwhile, we wish to explore the country. It is a charming neighbourhood, although very quiet in many respects.”

Mildred agreed and then began to plan excursions to this place and that, with the idea of making the stay of the visitors at Sheepeak pleasant. So agreeably did she behave and took such trouble in designing trips that Mrs. Bolstreath revised her opinion and began to believe that so nice a girl could not possibly know of Mrs. Jarsell’s doings, whatever knowledge her uncle might be possessed of.

And Dan, walking at top speed along the high road in a vain attempt to quieten his mind, was convinced that the inventor had some such knowledge. The idea which had brought him to his feet, and had sent him out to work off his excitement, was that the inventor was responsible for Mrs. Jarsell’s presence in London at unexpected moments. She financed him and retained him at her elbow, so to speak, that she might utilise his capabilities and his clever inventions. If, on the day of the London to York race, Mrs. Jarsell was at The Peacock Hotel about the hour of nine o’clock — as she certainly was on the evidence of Mrs. Pelgrin, who had no obvious reason to tell a lie — she could not have got to London by train or motor in time to murder Durwin. Yet she was assuredly at Blackheath, if the cinematograph was to be believed. Dan had hitherto been puzzled to reconcile apparent impossibilities, but at tea-time the solution of the problem had suddenly flashed into his mind. Mrs. Jarsell had travelled to town on an aeroplane.

“It is about one hundred and sixty miles from this place to town,” muttered Dan, walking very fast, and talking aloud to himself in his excitement, “so she could accomplish that distance with ease in three hours, considering that Vincent’s machine can fly at sixty miles in sixty minutes. He said so and I proved that he spoke truly when I experimented with the machine he lent me. Mrs. Jarsell was at The Peacock Hotel at nine o’clock, and the cinematograph showed she was at Blackheath at one o’clock. The race started then, and Durwin was killed shortly afterwards. Sixty miles an hour means one hundred and eighty miles in three hours. Say she started at half-past nine — which she could easily do. Leaving Mrs. Pelgrin immediately for Vincent’s place — she could reach London by half-past twelve, if not earlier, seeing she had just one hundred and sixty miles to go. There would be no difficulty in her reaching Blackheath and stabbing Durwin at the time the death took place; and, of course, had she travelled from Sheepeak to Thawley to catch the London express at nine o’clock, she could not have been at The Peacock Hotel at that hour. The aeroplane had been used to establish an alibi.”

Halliday was convinced that in this way the miracle of Mrs. Jarsell had taken place. No other means of transit could have landed her at the place where Durwin had met with his death. Of course, this assumption intimated that Mrs. Jarsell was an accomplished aviator, and that there had been no hitch in the journey from Sheepeak to Blackheath. But these were not impossibilities, for Vincent probably had taught the woman how to fly, and perhaps had handled the machine himself. There was room for two in the aeroplane, as Dan very well knew, since he had taken Penn for a flight himself, and the vehicle used was probably built on the same lines as the one lent. Since aviation was yet in its infancy there was certainly a possibility that such a journey could not take place without accidents or hindrance. But, as inferior machines had accomplished greater distances, Dan quite believed that Mrs. Jarsell, with or without Vincent as pilot, had reached London in one smooth stretch of flying. On other occasions she might not have been so successful, but on this one she probably had, for to get to Blackheath in time to commit the crime it would have been necessary for her to use rightfully every second of the given time. No wonder with such a means of transit at her disposal she could prove an advantageous alibi, when occasion demanded. Also, since the late conquest of the air afforded her the opportunity of swift travelling, greatly in excess of other human inventions, it was quite reasonable that she should live so far from the scene of her criminal exploits.

Thinking thus, Halliday stumbled across the very person who was in his thought. He rushed with bent head along the roads and unconsciously mounted towards the vast spaces of the moorlands, stretching under grey skies. Thus — and he swiftly decided that the collision was meant — he ran into Mrs. Jarsell, who approached in the opposite direction. She laughed and expostulated, as if Dan was in the wrong, although she must have seen him coming, and the road was wide enough for her to move to one side.

“Really, Mr. Halliday, you require the whole country to move in,” said Mrs. Jarsell in her heavy way, and with an affectation of joviality.

“I— I— I beg pardon,” stammered Dan, not quite himself, and stared at her as though she had suddenly risen out of the earth. Indeed, so far as he was concerned, she had done so, ignorant as he was of her approach.

The woman was arrayed in her favourite white, but as the day was chilly, she wore a voluminous cloak of scarlet silk quilted and padded and warm both in looks and wear. Her black eyes, set in her olive-hued face, peered from under her white hair as watchfully as ever. At the present moment, her heavy countenance wore an expression of amusement at the startled looks of the young man, and she commented on them with ponderous jocularity.

“One would think I was a ghost, Mr. Halliday. You will admit that I a............