And he turned as if to approach the door.

For an instant the woman hesitated, and Brett thought that he had scored.

"Wait," she said, lowering her voice, though there was still the menace of subdued passion in her accents. "Who is your friend?"

"A gentleman whose identity in no way concerns you. You must deal with me, and it will be better if you ask who I am."

"I know," she said, laconically. "Come this way, both of you."

She raised a flap-door located at one side of the counter. Brett followed her into a passage behind the doorway that led into the bar. Fairholme succeeded him.

The trio passed rapidly through a door at the end of the passage, and quickly found themselves in a long, low room, usually devoted to billiards. The place was dark and smelled evilly of stale tobacco. Daylight penetrated but feebly through the red blinds that blocked up three windows on one side. The woman drew two of these blinds, and thus illuminated the interior. The windows opened on to a yard, and the place was thoroughly shut off from all observation from the street.

"Now," she said, "I will show you something."

She walked towards the fireplace at the end of the room. On the mantelpiece was a square of iron sheeting, painted white and studded with curious-looking spikes in circles, triangles, and straight lines. From a box close at hand she took half a dozen small glass bulbs, red and blue. She placed them in a line on some of the spikes at intervals of two inches. Then she retired to that side of the room where they had entered. The distance was perhaps thirty feet.

Before Brett or Fairholme could vaguely guess her intention she whipped a revolver out of her pocket. It would be idle to deny that they were startled, but the woman paid not the least attention to them.