I felt my ears turning red, but Manning never budged. He could have raised Cain with her, confined her to her quarters, maybe even have court - martialed her, but Manning isn't like that. He told me once that every time a man is court - martialed, it is a sure sign that some senior officer hasn't measured up to his job. "I am sorry you feel that way, Doctor," he said mildly, "and I agree that my technical knowledge isn't what it might be. And, believe me, I do wish that healing were all we had to worry about. In any case, I have not refused your request. Let's walk over to your laboratory and see what the problem is. Likely there is some arrangement that can be made which will satisfy everybody.

He was already up and getting out his greatcoat. Her set mouth relaxed a trifle and she answered, "Very well. I'm sorry I spoke as I did."

"Not at all," he replied. "These are worrying times. Come along, John." I trailed after them, stopping in the outer office to get my own coat and to stuff my notebook in a pocket.

By the time we had trudged through mushy snow the eighth of a mile to her lab they were talking about gardening!

Manning acknowledged the sentry's challenge with a wave of his hand and we entered the building. He started casually on into the inner lab, but Karst stopped him. "Armor first, Colonel."

We had trouble finding overshoes that would fit over Manning's boots, which he persisted in wearing, despite the new uniform regulations, and he wanted to omit the foot protection, but Karst would not hear of it. She called in a couple of her assistants who made jury - rigged moccasins out of some soft - lead sheeting. The helmets were different from those used in the explosives lab, being fitted with inhalers. "What's this?" inquired Manning.

"Radioactive dust guard," she said. "It's absolutely essential."

We threaded a lead - lined meander and arrived at the workroom door which she opened by combination. I blinked at the sudden bright illumination and noticed the air was filled with little shiny motes.

"Hm - m - m - it is dusty," agreed Manning. "Isn't there some way of controlling that?" His voice sounded muffled from behind the dust mask.

"The last stage has to be exposed to air," explained Karst. "The hood gets most of it. We could control it, but it would mean a quite expensive new installation."

"No trouble about that. We're not on a budget, you know, It must be very annoying to have to work in a mask like this."

"It is," acknowledged Karst. "The kind of gear it would take would enable us to work without body armor, too. That would be a comfort."

I suddenly had a picture of the kind of thing these researchers put up with. I am a fair - sized man, yet I found that armor heavy to carry around. Estelle Karst was a small woman, yet she was willing to work maybe fourteen hours, day after day, in an outfit which was about as comfortable as a diving suit. But she had not complained.

Not all the heroes are in the headlines. These radiation experts not only ran the chance of cancer and nasty radioaction burns, but the men stood a chance of damaging their germ plasm and then having their wives present them with something horrid in the way of offspring - no chin, for example, and long hairy ears. Nevertheless, they went right ahead and never seemed to get irritated unless something held up their work.

Dr. Karst was past the age when she would be likely to be concerned personally about progeny, but the principle applies.

I wandered around, looking at the unlikely apparatus she used to get her results, fascinated as always by my failure to recognize much that reminded me of the physics laboratory I had known when I was an undergraduate, and being careful not to touch anything. Karst started explaining to Manning what she was doing and why, but I knew that it was useless for me to try to follow that technical stuff. If Manning wanted notes, he would dictate them. My attention was caught by a big boxlike contraption in one corner of the room. It had a hopperlike gadget on one side and I could hear a sound from it like the whirring of a fan with a background of running water. It intrigued me. I moved back to the neighborhood of Dr. Karst and the Colonel and heard her saying, "The problem amounts to this, Colonel: I am getting a much more highly radioactive end product than I want, but there is considerable variation in the half - life of otherwise equivalent samples. That suggests to me that I am using a mixture of isotopes, but I haven't been able to prove it. And frankly, I do not know enough about that end of the field to be sure of sufficient refinement in my methods. I need Dr. Obre's help on that."

I think those were her words, but I may not be doing her justice, not being a physicist. I understood the part about "half - life." All radioactive materials keep right on radiating until they turn into something else, which takes theoretically forever. As a matter of practice their periods, or "lives," are described in terms of how long it takes the original radiation to drop to one-half strength. That time is called a "half - life" and each radioactive isotope of an element has its own specific characteristic half - lifetime.

One of the staff - I forget which one - told me once that any form of matter can be considered as radioactive in some degree; it's a question of intensity and period, or half - life.

"I'll talk to Dr. Ridpath," Manning answered her, "and see what can be arranged. In the meantime you might draw up plans for what you want to reequip your laboratory."

"Thank you, Colonel."

I could see that Manning was about ready to leave, having pacified her; I was still curious about the big box that gave out the odd noises.

"May I ask what that is, Doctor?"

"Oh, that? That's an air conditioner."

"Odd - looking one. I've never seen one like it."

"It's not to condition the air of this room. It's to remove the radioactive dust before the exhaust air goes outdoors. We wash the dust out of the foul air."

"Where does the water go?"

"Down the drain. Out into the bay eventually, I suppose.

I tried to snap my fingers, which was impossible because of the lead mittens. "That accounts for it, Colonel!"

"Accounts for what?"

"Accounts for those accusing notes we've been getting from the Bureau of Fisheries. This poisonous dust is being carried out into Chesapeake Bay and is killing the fish."

Manning turned to Karst. "Do you think that possible, Doctor?"

I could see her brows draw together through the window in her helmet. "I hadn't thought about it," she admitted. "I'd have to do some figuring on the possible concentrations before I could give you a definite answer. But it is possible - yes. However," she added anxiously, "it would be simple enough to divert this drain to a sink hole of some sort."

"Hm - m - m - yes." He did not say anything for some minutes, simply stood there, looking at the box.

Presently he said, "This dust is pretty lethal?"

"Quite lethal, Colonel." There was another long silence.

At last I gathered he had made up his mind about something for he said decisively, "I am going to see to it that you get Obre's assistance, Doctor - "

"Oh, good!"

" - but I want you to help me in return. I am very much interested in this research of yours, but I want it carried on with a little broader scope. I want you to investigate for maxima both in period and intensity as well as for minima. I want you to drop the strictly utilitarian approach and make an exhaustive research along lines which we will work out in greater detail later."

She started to say something but he cut in ahead of her. "A really thorough program of research should prove more helpful in the long run to your original purpose than a more narrow one. And I shall make it my business to expedite every possible facility for such a research. I think we may turn up a number of interesting things."