They distinctly heard him open the door, and as distinctly heard him close it again.
"You wait here, Marigold," the young fellow whispered. "I'll creep up and see what I can. Perhaps I shall hear them talking."
"Yes, do," she said. "But take the greatest care. Mind the stairs don't creak. He'll be alarmed in a moment."
"Leave that to me," he replied, and next moment he left her side, and slowly ascending the few remaining steps, gained the hall, and then the foot of the stairs which led to the first floor.
Though he had not removed his shoes he made no noise, for he trod slowly and cautiously, never lifting one foot until the other was down silently. Thus very slowly he followed the mysterious man in white.
Hardly had he ascended four steps when an electric bell sounded, apparently in the locked room. He halted, and in an instant decided to retreat. Scarcely before Marigold had realised that the alarm had sounded, he sprang down, rejoined her, and whispering:
"Quick! Let's get down!" he descended into the dark kitchen. There, clutching her by the arm, he felt his way to the door.
Without pausing to listen to the effect of the alarm upon the man upstairs, the pair passed out into the area, closed the door after them, hurried up the steps, and out into the street.
"Let's get away before he sees us!" Gerald urged, and they both ran light-footed along to the corner into King Street, where they escaped.
"There's a trap in that house!" Durrant declared, as after hurrying breathlessly they walked along in the direction of the Broadway Station. "Upon one of those stairs is an electrical contact which gives to the locked room the alarm of an intruder. He switched it on from his room below!"
"Yes!" said the girl. "I feel sure there is."
"And that shows that there's something very wrong somewhere. Mr. Boyne has, in secret, a guest who is in hiding upstairs. He takes him food and water every night as we have seen with our own eyes. And, further, he had taken the precaution of installing an electrical alarm in case anyone followed him upstairs while he was there with his friend."
"True," said the girl. "But why does he disguise himself whenever he goes up there?"
"That we cannot yet tell. At present it is a complete mystery."
"And a most uncanny one!"
"It is, I can't see the motive of that disguise."
"Is it not weird? He was covered from head to foot in that white cloak, and only those two slits for his eyes."
"Yes. And he moved as silently as a shadow."
So the pair conversed until they reached the Broadway Station, and left by the Underground a few moments later.
What they had witnessed that night had increased the mystery a hundredfold.
In the meantime Bernard Boyne had been startled by the ringing of the bell, yet in the full knowledge that Mrs. Felmore could hear nothing. That secret alarm had, as a matter of fact, been installed with his own hands about two months before, with its switch concealed in the upstairs room.
On hearing it, he instantly flung off his white cloak and dashed headlong down the stairs.
In the hall, however, he halted and burst out laughing.
"Fool you are, Bernard!" he exclaimed aloud to himself. "Yes, you are getting more nervous every day!"
The reason of this was because close to the front door sat Mrs. Felmore's black cat, waiting to be let out for the night.
"Ah, pussy!" he exclaimed. "So it is you who ran silently down the stairs and set off the gong, eh?"
And, opening the door, he let out the cat, saying:
"Out you go, Jimmy, and don't do it again."
Then he reascended the stairs to the locked room, perfectly satisfied with the solution of what a few moments before had caused him very considerable alarm.
No intruder would be tolerated in that dingy house the house of great mystery.
He carried in his hand a small bottle of meat extract which he had taken from the sideboard in the parlour, and was fully satisfied that it was the cat who had set off the alarm.
As Gerald and Marigold sat side by side in the train, they could not converse because of the noise, but at Earl's Court, where they changed, the girl for Wimbledon Park and her lover bound in the opposite direction, Marigold halted on the platform, and said:
"I feel worried about auntie, Gerald. There's something wrong in that house. Don't you think so?"
"Frankly, I do," was the young man's reply. "That he sets an alarm when he visits the mysterious person concealed in that locked room is in itself a most remarkable feature of the affair, which is one we must certainly probe to the bottom."
"But Mr. Boyne is such a nice man. Everyone speaks so well of him. In all Hammersmith I don't think he has a single enemy, save those who are jealous of his local popularity. And there are always such."
"As I've said before, Marigold, the men who are deep schemers always take care to establish a high reputation locally. This Mr. Boyne has, no doubt, done so with some ulterior motive."
"And that motive we mean to find out," said the girl decisively.
"We will," he said, in a hard voice. "I feel confident that we are on the track of some very sensational affair."
"Who can be the person who is hiding?"
"Ah! that remains to be seen. It is evidently someone who dare not show his face not only in the light of day, but even at night."
"But why does Mr. Boyne wear that hideous robe with slits for the eyes?" asked Marigold, bewildered, as they walked to the stairs.
"At present, I can't imagine. But we shall know the truth very soon, never fear," the young man replied. And then, lifting his hat politely, he shook her hand, and they parted after a very adventurous evening.
As Gerald Durrant travelled back to his home, he reflected deeply upon the whole affair. Though he had not dared to mention the fact to Marigold, he was more deeply in love with her than ever. She was the most dainty and most beautiful girl he had ever met. She was chic to the finger-tips, and among the many girl clerks he met daily she was outstanding on account of her refinement, her modesty, and the sweet expression always upon her countenance.
Yet the problem which she had put forward to him was certainly an inscrutable one. Boyne, the highly respectable, hard-working insurance agent, lived in that dingy and rather stuffy house surrounded by meagre comfort which, in itself, betokened modest means. For every penny Bernard Boyne gained he worked very hard. Insurance agency is not highly-paid, for everything is nowadays cut to a minimum, while since the war the cost of living has soared.
Nevertheless, as he sat in the train taking him westward, he examined the facts. Boyne employed as housekeeper a woman who was stone-deaf. Why? Was it because the person confined behind that stout door upstairs sometimes shouted and made noises which would have attracted the attention of any person who possessed the sense of hearing?
That this was so he was convinced. Had it not been proved by Boyne carrying food to the mysterious person who was his captive, or who remained in voluntary concealment?
If the latter, why did he disguise himself each time he paid him a visit?
No. Somebody was held there captive against his will, and the reason of the wearing of that cloak was in order that the captor should remain unknown and unidentified. Truly, there was an element of sensationalism in the whole affair!
He was, however, determined to get to the bottom of it. Marigold had, in her perplexity, consulted him, and he had given his aid. Now, having witnessed what he had, he meant to carry the affair through, and solve the mystery of Bernard Boyne and his locked room in Hammersmith.
It occurred to him that perhaps by watching Boyne's movements he might learn something of interest. The unfortunate part of it was that in his position he was engaged all day, and could never have any time to devote to the affair till six or seven o'clock. Nevertheless, he had made a firm resolve to discover the reason of that locked room, and the identity of the person concealed within.