“You know, Snake-child, I once had a mule that was a good stud. It happens sometimes. Maybe this time.”

“Maybe,” Snake said. The chance that her pony’s immunities had left him fertile was no more remote than the chance of getting a fertile mule: Snake did not feel she was deceiving Grum with her cautious agreement.

Snake returned to her tent, let Sand out of the serpent case, and milked him of his venom. He did not fight the process. Holding him behind the head, she squeezed his mouth open gently and poured a vial of catalyst down his throat. He was much easier to drug than Mist. He would simply coil up sleepily in his compartment, little different from normal, while the poison glands manufactured a complicated chemical soup of several proteins, antibodies for a number of endemic diseases, stimulants to the immune systems of human beings. Healers had been using rattlers much longer than they had had cobras; compared to Mist, the diamondback was tens of generations and hundreds of genetic experiments more adapted to catalytic drugs and their changes.

In the morning, Snake milked Sand into a serum bottle. She could not use him to administer the vaccine, for each person required only a small amount. Sand would inject too much of it too deeply. For vaccinations, she used an inoculator, an instrument with a circle of short, needle-sharp points that pressed the vaccine down just beneath the skin. She returned the rattler to his compartment and went outside.

The people from the camps had begun to gather, adults and children, three or four generations in each family. Grum stood first in line with all her grandchildren around her. Altogether there were seven, from Pauli, the oldest, to a child about six, the little girl who had polished Swift’s tack. They were not all Grum’s direct descendants, for her clan’s organization depended on a more extended family. The children of her long-deceased partner’s siblings, of her sister, and of her sister’s partner’s siblings, were equally considered her grandchildren. All those people had not come with her, only those who were her apprentices as future caravannaires.

“Who’s first?” Snake asked cheerfully.

“Me,” Grum said. “I said me, so me it is.” She glanced at the collectors, who stood in a colorful huddle off to one side. “You watch, Ao!” she called to the one who had asked for Snake’s broken gear. “You’ll see it doesn’t kill me.”

“Nothing could kill you, old rawhide-skin. I wait to see what happens to the others.”

“ ‘Old rawhide-skin’? Ao, you old ragbag!”

“Never mind,” Snake said. She raised her voice slightly. “I want to tell you all two things. First, some people are sensitive to the serum. If the mark turns bright red, if it hurts sharply, if the skin is hot, come back. I’ll be here till evening. If anything is going to happen it’ll happen before then, all right? If someone’s sensitive I can keep them from getting sick. It’s very important that you come to me if you feel anything worse than a dull ache. Don’t try to be brave about it.”

Among the nods and agreements Ao spoke up again. “This says you might kill.”

“Are you foolish enough to pretend nothing’s wrong if you break your leg?”

Ao snorted in derision.

“Then you’re not foolish enough to pretend nothing’s wrong and let yourself die if you overreact.” Snake took off her robe and pushed up the very short sleeve of her tunic. “The second thing is this. The vaccination leaves a small scar, like this one.” She went from group to group, showing them the mark of her first immunization against venom. “So if anyone wants the scar in a place less obvious, please tell me now.”

Seeing the tiny innocuous scar calmed even Ao, who muttered without conviction that healers could stand any poison, and then shut up.

Grum came first in line, and Snake was surprised to see she was pale. “Grum, are you all right?”

“It’s blood,” Grum said. “Must be, Snake-child. I don’t like to see blood.”

“You’ll hardly see any. Just let yourself relax.” Talking to Grum in a soothing voice, Snake swabbed the old woman’s arm with alcohol-iodine. She had only one bottle of the disinfectant left in the medicine compartment of the serpent case, but that was enough for today and she could get more at the chemist’s in Mountainside. Snake squeezed a drop of serum onto Grum’s upper arm and pressed the inoculator through it into her skin.

Grum flinched when the points entered, but her expression did not change. Snake put the inoculator into alcohol-iodine and swabbed Grum’s arm again.

“There.”

Grum peered at her in surprise, then glanced down at her shoulder. The pinpricks were bright red but not bleeding. “No more?”

“That’s all.”

Grum smiled and turned toward Ao. “You see, old pothole, it’s nothing.”

“We wait,” Ao said.

The morning progressed smoothly. A few of the children cried, more because of the sting of the alcohol than the shallow pricks of the inoculator. Pauli had offered to help, and amused the little ones with stories and jokes while Snake worked. Most of the children, and not a few of the adults, remained to listen to Pauli after Snake had vaccinated them.

Apparently Ao and the other collectors were reassured about the safety of the vaccine, for no one had yet fallen down dead when their turn came. They submitted stoically to needle pricks and alcohol sting.

“No lockjaw?” Ao said again.

“This will protect you for ten years or so. After that it’s safest to get another vaccination.”

Snake pressed the inoculator against Ao’s arm, then swabbed the skin. After a moment of grim hesitation, Ao smiled, for the first time, a wide, delighted smile. “We fear lockjaw. An evil disease. Slow. Painful.”

“Yes,” Snake said. “Do you know what causes it?”

Ao put one forefinger against the palm of the other hand and made a skewering gesture. “We are careful, but…”

Snake nodded. She could see how the collectors might get serious puncture wounds more often than other people, considering their work. But Ao knew the connection between the injury and the disease; a lecture about it would be patronizing.

“We never see healers before. Not on this side of the desert. People from other side tell us.”

“Well, we’re mountain people,” Snake said. “We don’t know much about the desert, so not many of us come here.” That was only partly true, but it was the easiest explanation to give.

“None before you. You first.”

“Maybe.”

“Why?”

“I was curious. I thought I might be useful.”

“You tell others to come too. No danger for them.” Suddenly the expression on Ao’s weather-creased face darkened. “Crazies, yes, but no more than in mountains. Crazies everywhere.”

“I know.”

“Sometime we find him.”

“Will you do one thing for me, Ao?”

“Anything.”

“The crazy took nothing but my maps and my journal. I suppose he’ll keep the maps if he’s sane enough to use them, but the journal’s worthless to anyone but me. Maybe he’ll throw it away and your people will find it.”

“We keep it for you!”

“That’s what I’d like.” She described the journal. “Before I leave I’ll give you a letter for the healers’ station in the north mountains. If a messenger going that way took the journal and the letter there they’d be sure to get paid.”

“We look. We find many things but not books too often.”

“Probably it’ll never turn up, I know that. Or the crazy thought it was something valuable and burned it when he realized it wasn’t.”

Ao flinched at the thought of perfectly good paper being burned to nothing. “We look hard.”

“Thank you.”

Ao went off after the other collectors.

As Pauli finished the story of Toad and the Three Tree Frogs, Snake checked the children and was glad not to find the swelling and redness of any allergic reactions.