The girl stood motionless, her eyes wide, straining for some tangible thought, and as she so stood, staring into the older woman's face, Saul noticed the bottles in Cloud's arms and asked abruptly, "What are you doing with the 511?"
Cloud hesitated and glanced at Whittly. The old doctor nodded.
"Yes, tell him. It's time he knew."
"Time I knew what?" Saul's eyes bored into Cloud's.
"Why, it may amount to nothing, Saul, but Whittly tells me the town is pretty badly aroused, up in arms over the laboratory." Helene caught her breath in a sharp gasp, and her gaze leaped to Saul's great slate-gray eyes, but Cloud went on quietly: "They don't like it because we've been so secretive, and are imagining all sorts of ridiculously horrible things as going on out here. They threaten to come out and wreck the place. Doc and I thought we'd better move the solution to the garage where it would be safe in case the people should become fanatical enough to mob the buildings. We've moved it all but this."
"I want to see a bottle of it!" Helene's voice cut in, and she stepped toward Cloud, holding out her hand. Wonderingly Cloud gave her one of thé small bottles, and she turned it over in her fingers, looking at it closely. Suddenly she wheeled on Saul. "Where's the bottle Henry used? Get it, quickly!"
"Why? What does it matter which he used?" Saul frowned in puzzlement. "They're all alike."
"Don't question her," Mrs. Blauvette commanded, her eyes still on the girl's face. "I tell you she was sent; go get her the bottle. It's on the window-sill in Henry's room, where he left it."
Saul started in surprize, but went to get the bottle without a backward look, and three pairs of eyes centered on Helene intently, as though awaiting some miracle, as he returned and placed the bottle in her hand. She examined it closely, holding it up to the other one she had received from Cloud. The two bottles were identical, both numbered plainly in small inked figures, 511. She put them both in her left hand, holding her forefinger between them to keep from confusing them with each other, and pulled the corks with her right hand. She sniffed lightly at the small glass necks, and abruptly her eyes lit with a high light. Again she wheeled on Saul.
"How did it act on Henry Arn? Tell me!"
"It acted exactly as 510 acted on the animals," Saul answered, dazed by the expression on her face.
"Yes, it certainly did," Cloud put in. "I can vouch for that. Mrs. Blauvette can verify that that is what I told her a while ago."
"Oh, there's no doubt of its action," Saul returned. "If it had been 510 that Henry took, I'd know that we'd won the day. I'd know beyond all doubt that the action carried through into humans precisely the same. Helene! What is it? What do you think? What do you know?"
"It was 510 that Henry used!" The girl held the two bottles toward him, her eyes aflame. "Smell them—the one Henry used contains no ether!"
With a loud cry Saul leaped toward her and snatched the bottles, raising them alternately to his nostrils.
"God!" He turned a whitened countenance to his mother. "She's right! See that small bubble—that flaw on the edge of this bottle-neck? It's queerly shaped—like a cross. I remember! I took this bottle down to empty the 510 out of it and refill it with 511. John called me out, and I went and left it standing there. I'd already marked it 511, and we were so badly used up and excited that I
