It was Wanda Lindstrom who answered the selectman, with her quiet authority. “Dr. Hubbard and I hope you are exactly right, Mr. Scott. And I agree it may not be necessary to take drastic action like clearing people out . . .” Her gray eyes bore into the man’s as she added a signal word, “Yet.” Then she said to the others, “But we had all better recognize that evacuation may become necessary if our surmise about a mutation should prove correct.”

“There it goes again!” Scott muttered. Aloud he complained; “I’d still like to know what you mean by that.”

Peter Hubbard intervened. To Elizabeth, it seemed he wanted to shield Wanda Lindstrom from harassment by Stephen Scott. She was embarrassed, herself, at the belligerence the man was displaying. Why, Scott was almost making it sound as if Yarkie’s trouble was Wanda Lindstrom’s fault. Elizabeth’s admiration of the woman had been growing throughout the difficult session. She could only respect her self-­possession.

Peter Hubbard was being patient with Stephen Scott. “I’m sorry if we seem to be getting ahead of ourselves, sir. I’m glad you asked about mutation, because it may not be clear to others as well.” He did not wait for a response. “The word, of course, means a change. In biology it means a sudden variation in a form of life—in this case possibly the cockroaches—usually when something abnormal happens in the basic genes. Then a new form of the species is created. It might just die out—as happens with freaks such as you sometimes see in circuses. Or it sometimes persists and gives birth to more individuals with the new characteristics until a new species is, in effect, established . . .”

It was Elizabeth who interrupted, raising her hand as if she were attending a schoolroom lecture. “What causes the genes to change?”

“I don’t want to get technical,” Hubbard answered, “but we do know that chemicals can start a mutation chain going. We call them ‘mutagens.’ They work by interfering with the normal DNA bases that ordinarily control development. . . .”

Elizabeth responded thoughtfully, “And some chemical combinations in the dump may have caused ‘mutagens’ affecting the cockroaches?”

“That’s one possibility, yes,” Wanda Lindstrom answered her.

Russell Homer, following in sheer fascination, expressed an immediate thought, “But I only changed the poisons a couple of weeks ago. Could the ‘mutation’ happen that fast?”

Hubbard declared, “Good point. The process would have to be going on for a long time. I mean, although the first mutation would have been a sudden variation, it would have taken years for the mutated group to prevail and multiply in the numbers your reports indicate.”

Almost with relief, Homer said, “Then it probably wasn’t the new stuff I spread out there?”