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!"