Garth drew him to the sidewalk.

"If you waste time steering me wrong," he said, "I'm through. And don't forget I have a gun. Try to throw me down once we're in, I'll use it."

Black made an effort to square his shoulders. He crossed the avenue with a lurching gait. Garth glanced back. A dark figure skulked after them.

So that was all right. The inspector would know their destination immediately.

"One thing," Garth asked. "How did you have the nerve to drive your limousine to the place last night?"

"I didn't," Black answered. "I picked it up in Third Avenue."

He did not speak again, and Garth no longer urged him. He walked straight for the block in which he had been at his folly last night. But he did not pause there. He continued across Lexington Avenue and made confidently for the deserted, dust-filled house which just now had mocked the police. Garth, amazed, followed him to the bas.e.m.e.nt door.

Black took a key from his pocket, and with the ease of long habit inserted it through the obscurity in the lock. The door opened and Garth walked into the blackness with a quickening suspense. His apprehension was for Nora rather than himself. What had happened to her when she had stepped into the dusty hall? Her only chance was that he would not be caught in this somber pit as she had probably been. He put his hand on his revolver.

"Go first," he whispered.

The darkness was so complete that Garth had to keep his fingers on the other's arm to avoid stumbling against the walls. Yet his guide went with a quick a.s.surance to the rear door which he opened with another key. They stepped beneath a rough shelter of corrugated iron such as is hastily thrown up for the protection in summer of washboards, or, in winter, for the storing of wood. Black proceeded beneath this shelter along the fence to the corner. Garth noticed a large acc.u.mulation of rubbish in the yard, souvenirs, doubtless, of indolent and utilitarian neighbors.

Black stooped. Evidently he had given a signal which Garth had not seen or heard, for straightway he arose and leant against the fence, waiting.

"What now?" Garth asked.

Black raised his finger to his lips.

Garth looked down at a rustling among the rubbish. A thin piece of flagging had opened at his feet as if hinged like a trap-door, leaving visible the top of a flight of rough wooden steps.

Black stepped down and Garth followed. The steps led diagonally under the angle of the fence. Others rose into the corner of the adjacent yard. If this was their destination it was neither to one side nor directly behind the empty house used as an entrance. Garth marvelled at the simplicity of the contrivance. Two men in half a day could have accomplished the entire excavation and arranged the steps. Moreover, without a definite clue the police would never suspect such an entrance.

While Black carefully lowered the flag on the other side Garth glanced around. They stood in the kitchen shed of a house which, of course, faced the next street. Garth had no doubt that the place was masked with a physician's office, or, perhaps, an appeal for boarders, who, nevertheless, would always fail to find rooms available at the hour of their application. He saw nothing of the man who had admitted them by raising the flag. He was more disturbed than before, since he could picture the inspector's bewilderment on learning that he had entered the house which had been so recently raided and combed.

Garth had small time for speculation. He saw Black press an electric b.u.t.ton. Faintly he heard the response from a m.u.f.fled bell--two rings short, and one long. Almost at once the door opened a crack, but no gleam of light came through. Black muttered something unintelligible to Garth, and led him into a darkness as complete as that which had oppressed him in the empty house. Yet in spite of it he was sure it was a woman who had admitted them.

"This way," Black said.

Garth followed, scarcely breathing. Where would he find Nora? How would he find her?

A door opened ahead, and at last there was a light--a subdued, brown light, unhealthy, suggestive of a melancholy repose.

Black went first, then Garth, into an inner hallway, which was saturated with this aberrant radiance.

Garth turned sharply to inspect the woman who had followed them in. He drew back. He controlled his gasp of relief and grat.i.tude, for it was Nora herself who had opened the door for them and who stood now on the threshold of the hall. Yet he saw that his presence, instead of bringing to them a grateful welcome, had drawn into her eyes a fear which quickly approached despair.

She wore the ap.r.o.n and the cap of a housemaid, transparent hints as to how she had found an entrance and remained here, unmolested. Her features, in addition, were subtly changed, so that one, less acquainted with them than Garth, might have pa.s.sed her unrecognizing.

His astonishment had held him longer than was discreet. He turned at a sound to find his conductor gone. He knew what that portended. He cursed his carelessness.

Nora took his arm.

"What are you doing here?" she whispered tensely. "Go before it's too late. I knew they suspected trouble to-night, but I never dreamed of your getting in here alone. Go--the way you came."

"To be caught in the yard?" he scoffed. "That fellow's given me away by this time. They'll watch that exit first."

He ran along the hallway. The strange brown light appeared to have given the air a substantial resistance. He breathed it with distaste. It choked him. At the foot of the stairs Nora caught his arm again.

"Where are you going?"

"Up there," he answered. "I haven't the ghost of a show in this suffocating bas.e.m.e.nt. They'll look for me here first."

He climbed the stairs. She followed him.

"Jim," she breathed, "it's hopeless. They'll never let you out."

He turned at the head of the stairs. The same dim, unreal light was repugnant in his lungs here. A repellent odor, not to be cla.s.sified, crept into his nostrils, made him want to cough. Heavy purple hangings were draped across two doorways.

"Tell me the lay-out," he whispered. "Quick! The yard isn't the only getaway?"

"Except the roof and the front," she whispered back, "and they're locked. The head one keeps the keys. For G.o.d's sake, Jim, try to get out of this house before it's too late."

He pointed to one of the draped doorways. It was at the end of the hall, but the hall appeared to him too short.

"Is that the front door?"

She shook her head.

"Only leads to the front of the house. That's planted, of course--a boarding house. I tell you that door's locked."

"Then how can I get to a front window?"

"You can't, Jim."

He tried to plan.

"Then how am I--"

A heavy step seemed to set the thick, brown air in lazy motion. It came from a nearby room. It approached. Garth glanced at the purple hangings, expecting them to part on one who would discipline without mercy his presumption.

"Jim! They've got you, and if they see me with you--"

She spread her arms.

"They know you're a detective. Your only hope is that they shouldn't suspect me. And I can't lose all I've done. Hit me, Jim."

"Nora!"

"Trust me," she begged, "and we've a chance. They mustn't doubt me. Hit me, Jim. Take hold of me. Clap your hand over my mouth. Quick!"

He drew back. He knew she was right, but he couldn't, all at once, bring himself to obey.