afraid to come by herself?”
“That is about the size of it,” related the bronze man.
Just then, Monk Mayfair came up, carrying a rag which he had used to scour the barrel that had disgorged so much unpleasant smoke. It was a tattered smudge of charcoal black.
“We should see what this stuff is in a jiffy,” he related.
Doc and Ham followed the hairy chemist into the great laboratory, where the spectrometer was once again engaged.
The results were disappointing, as they discovered just a few minutes later. The residue was not anything more interesting than black gunpowder and some other chemicals.
“This don’t match the other stuff,” Monk mumbled in disappointment.
“What was the other stuff composed of?” Ham wanted to know.
“We have no clue, Doc and me,” admitted the homely chemist.
Ham Brooks seemed momentarily taken aback. He looked to Doc Savage for confirmation.
Doc told Ham, “The substance found in the hotel is unknown to us.”
“What about the greenish shadow on our hallway wall?” prompted Ham.
“We will turn our attention on that next.”
The three men returned to the reception room and filed out into the corridor, and were soon huddled around the yellow-green shadow.
It still discolored the marble wall unpleasantly, its aspect hideous. The wall consisted of greenish-black marble below its waist, while the facing above that was sandy in hue. The discoloration stood out starkly against both types of marble.
Monk took a chance, applied his wide nostrils to the unlovely splotch, and began sniffing.
“I don’t smell nothin’,” he admitted, mild voice puzzled.
Doc Savage had brought with him several vials of chemicals. Carefully, he began applying different substances at random points on the yellow-green shadow with a swab, changing swabs with every application.
They waited for the chemical reaction to take hold.
Surprisingly, nothing of the sort transpired.
Monk grunted, “Ain’t painted on. So what is it, then?”
No one knew what or how to answer, least of all Doc Savage.
“This deserves further study,” he said as they retreated to the reception room. “Which we will undertake with appropriate equipment, inasmuch as it is not practical to remove that section of the marble.”
No sooner had Doc closed the door behind them than the telephone commenced jangling.
Leaping, Ham scooped up the receiver. He listened for a few moments and said to the others, “It’s Long Tom.”
Doc accepted the telephone transmitter and said, “Go ahead, Long Tom.”
“I looked into this Ned Gamble fellow,” Long Tom reported. “He’s a mineralogist, of all things. Strictly small-time. Teaches at a local college. Doesn’t have a bad reputation, doesn’t have much a reputation at all. He’s on the young side. Maybe he hasn’t had time to accomplish much of anything.”
“Please get to the heart of the matter,” requested the bronze man.
“O.K.,” said Long Tom. “He’s known to people at this conference. In fact, he had been planning to attend. Obviously, that won’t happen now. Asking around the exposition, I found out that this Gamble is engaged to a woman named Janet Falcon. Miss Falcon is the secretary to Myer Sim. So they all tie in together.”
Doc’s trilling piped up briefly, then he asked, “Janet Falcon appears to be the one who sent Gamble to New York. But she refused to divulge the reason why over the telephone. Look her up, Long Tom. Talk to her. She is rather shaken up right now, but we must get to the bottom of this. So far three persons have died.”
“I’ll get right on it, Doc,” said Long Tom, hanging up abruptly.
The bronze man turned to the others and said, “While Long Tom is pursuing the Chicago angle, we will endeavor to discover who laid the trap outside our garage door.”
Monk scratched his bullet head, which was furred by rusty red bristles.
“How are we gonna do that?” he asked.
Instead of replying, the bronze man turned