“Hide,” he whispered suddenly to us.

Without another word, though for the life of me I could make nothing out of it, I pulled the policeman into a little angle of the wall nearby, while Craig slipped into a similar angle.

We waited a moment.  Nothing happened.  Had he been seeing things or hearing things, I wondered?

From our hidden vantage we could now see a square piece in the floor, perhaps five feet in diameter, slowly open up as though on a pivot.  Beneath it we could make out a tube-like hole, perhaps three feet across, with a covered top.  It slowly opened.

A weird and sinister figure of a man appeared.  Over his head he wore a peculiar helmet with hideous glass pieces over the eyes, and tubes that connected with a tank which he carried buckled to his back.  As he slowly dragged himself out, I could wonder only at the outlandish headgear.

Quickly he closed down the cover of the tube, but not before a vile effluvium seemed to escape, and penetrate even to us in our hiding places.  As he moved forward, Kennedy gave a flying leap at him, and we followed with a regular football interference.

It was the work of only a moment for us to subdue and hold him, while Craig ripped off the helmet.

It was Dan the Dude.

“What’s that thing?” I puffed, as I helped Craig with the headgear.

“An oxygen helmet,” he replied.  “There must be air down the tube that cannot be breathed.”

He went over to the tube.  Carefully he opened the top and gazed down, starting back a second later, with his face puckered up at the noxious odor.

“Sewer gas,” he ejaculated, as he slammed the cover down.  Then he added to the policeman, “Where do you suppose it comes from?”

“Why,” replied the officer, “the St. James Drain—­an old sewer—­is somewhere about these parts.”

Kennedy puckered his face as he gazed at our prisoner.  He reached down quickly and lifted something off the man’s coat.

“Golden hair,” he muttered.  “Elaine’s!”

A moment later he seized the man and shook him roughly.

“Where is she—­tell me?” he demanded.

The man snarled some kind of reply, refusing to say a word about her.

“Tell me,” repeated Kennedy.

“Humph!” snorted the prisoner, more close-mouthed than ever.

Kennedy was furious.  As he sent the man reeling away from him, he seized the oxygen helmet and began putting it on.  There was only one thing to do—­to follow the clue of the golden strands of hair.

Down into the pest hole he went, his head protected by the oxygen helmet.  As he cautiously took one step after another down a series of iron rungs inside the hole, he found that the water was up to his chest.  At the bottom of the perpendicular pit was a narrow low passage way, leading off.  It was just about big enough to get through, but he managed to grope along it.  He came at last to the main drain, an old stone-walled sewer, as murky a place as could well be imagined, filled with the foulest sewer gas.  He was hardly able to keep his feet in the swirling, bubbling water that swept past, almost up to his neck.