The young folks planted seeds the next afternoon when they came home from school. Then in the next few days, they could scarcely wait to see the first seedlings break through the soil. The little green crooks popped up the morning that Dr. Kenton was to leave on his expedition.  
The scientist said that the plants would grow rapidly and produce edible food within the next ten days. He gave the children instructions for tending the crops, and they memorized his directions.
 
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He had showed Jill, Ted, and Randy how to attend to the mechanical functions of the home and also how to run the boat. The three helped him to load his gear into the boat, and then stood by as Dr. Kenton bade farewell to his wife. There were tears in Mrs. Kenton’s eyes as she waved good-by from inside the house.
 
Yank watched the strange goings-on from in front of his own dwelling. He seemed to understand that Dr. Kenton was leaving, but he still had not made friends with him.
 
When they were all in the boat, Jill dropped a fuel pill into the tank, and Ted took the steering wheel. He skillfully guided the boat along the winding watercourse to Main Canal and along its length to the science building. They all helped unload the gear on the dock, and Dr. Kenton said that this was where they must part.
 
“You three will have to run things while I’m away,” the scientist told them. “You shouldn’t have any trouble, but if anything does happen, call headquarters for help. There’s one thing I want you to be sure to attend to. Bring the empty spare air cartridges in the closet down here and have them filled. You never know when you’ll need them.”
 
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“We’ll bring them tomorrow on our way to school,” Ted promised.
 
Jill hugged her father hard and long. Like her mother, she was tearful at his leaving. Ted, himself, felt a tug of dread. He wondered if the trip into the Martian wilds would be a successful one or whether, as in the case of Randy’s father, it would end in disaster.
 
The children went on to school. Ted was glad to be going because it would take his and Jill’s minds off the melancholy of their father’s departure.
 
Ted found the opening lesson particularly interesting. In it he learned facts about the extinct native Martians. Mr. Garland showed slides on some diggings that had unearthed bones of these early people. The bones had been organized to the best of Earth scientists’ ability, but many were missing, and the reconstructed figures were largely guesswork. Ted wondered if his father’s expedition would uncover more information on these mysterious ancient people.
 
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As the young Kentons and Randy started for home in the boat that afternoon, Jill complained of having a headache. Ted told her it was probably due to eyestrain from looking at the slides, and this seemed to satisfy her. But when Ted docked the boat at the house, Jill said she felt worse.
 
Yank came running out to greet them, but the boys were so concerned over Jill that they paid little attention to him. He stood off sulking and watched Ted help his sister out of the boat and through the air lock of their house.
 
“Mother, Jill is sick!” Ted called when they were inside.
 
Mrs. Kenton had been spraying the hose on the plastic floor and furniture. She turned it off and allowed the spring on the hose to pull it back into the wall opening. The water swirled through the drain in the center of the floor and disappeared in a matter of seconds.
 
“What’s wrong with her?” Mrs. Kenton asked in alarm.
 
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Ted helped Jill off with her helmet. He was shocked to see that her face was feverish and her eyes strangely bright. She wandered away from the others and slumped tiredly on the divan.
 
“Don’t lie on that rubber cushion, dear!” Mrs. Kenton cried. “It’s still wet. What on earth has she got?” Mrs. Kenton asked the boys.
 
“It looks to me like she’s got bog fever,” Randy offered.
 
“How could she catch fever?” Mrs. Kenton asked.
 
“There’s a virus that comes from the sand bogs and sometimes gets through the air valve of space suits,” Randy said.
 
“I’d better call a doctor at headquarters right away!” Mrs. Kenton declared.
 
She went to the radiophone and put through the call. She was told that all the doctors were out on calls and that it might be an hour before one could come. However, when a nurse on duty in the Medical Center learned about Jill’s symptoms, she gave instructions for caring for the girl until the doctor could come.
 
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As Mrs. Kenton switched off the phone, she said, “The nurse said that Jill should be put to bed and kept warm. Come on, Honey,” she added, helping Jill to her feet and leading her toward the guest room.
 
“Is the disease serious?” Ted asked Randy worriedly.
 
“It can be,” Randy answered soberly. “We’ll probably have to be quarantined,” he added.
 
“How long does bog fever last?” Ted asked.
 
“The crisis comes pretty quickly after the first attack,” Randy answered. “I remember, because a friend of mine had it. If they pass the crisis, they’re usually well in a few days.”
 
Ted was reluctant to ask th............