"Why," answered Bob, thoughtfully, "the high voltage causes a sort of electrical breakdown of the gas in the tube and it's apt to affect the receiving."

"Say, Bob's getting to be a regular blue stocking," commented Jimmy admiringly. "We'll have to get a move on to catch up with him."

"You bet _you_ will," said Herb, with insulting emphasis on the p.r.o.noun. However, Jimmy was too interested to notice.

"Let's reduce the voltage, Bob," Joe was saying eagerly. "We'll test out the theory."

"It isn't a theory," replied Bob, as he reduced the voltage and the blue glow disappeared as though by magic. "You can see for yourself that it's a fact."

This discussion led to others, and they sat for some time eagerly experimenting with their set. It was just as well that they did for they had just gone over to their cottage and thus were able to answer quickly the imperative summons that came to them a few minutes later.

In response to a knock on the door they found Mr. Salper standing outside in the bitter night air looking so white and shaken that they were startled.

He came just inside the door and spoke in quick, jerky sentences like a man talking in his sleep.

"My wife is dangerously ill," he said. "She seems so much worse tonight that there is imperative need of a doctor. There is no doctor up here, and in this weather it would take too long to summon one. The trained nurse who is with her suggests that we try to get in touch with a doctor by radio and ask his advice. The idea is far-fetched, but it seems about our only hope. If that fails----" he paused and Joe broke in eagerly.

"My father's a doctor, Mr. Salper," he said, and there was pride in his voice.

"A doctor, eh?" returned the broker quickly. "Oh, if only he were here!"

"I don't see how you are going to get hold of your father," broke in Herb. "He's in Clintonia. Even if he got our message, through Doctor Dale or somebody else with a receiving set, he couldn't send any message here."

"But he isn't in Clintonia!" shouted Joe, eagerly. "He went to Newark, New Jersey, to attend some sort of medical convention and see if he couldn't find out more about the epidemic that hit Clintonia."

"Newark!" came simultaneously from Joe's chums.

"Why, the big radio sending station is there!" exclaimed Bob.

"Why can't you send a message to that station and ask them to get hold of your father?" broke in Jimmy.

"Maybe I could do it," announced Joe. And then he looked at Bob.

"Perhaps you had better do the sending. You'll probably have to call them in code."

Bob was willing, but first he went up to tell his mother and father where he and his chums were going and beg them not to worry if they did not come back soon.

On the way to the radio station they stopped at the Salper bungalow, where the calm-faced nurse was waiting for them. She had left the Salper girls in charge of their mother, giving them minute instructions as to what to do, and was going with Mr. Salper in the hope that they might possibly secure medical advice by radio.

The station was finally reached. It looked deserted and gloomy at that hour of the night, and as Bob sent a call for help vibrating through the ether he felt a creepy sensation, as though he were, in some way, dealing with ghosts.

There was just the slightest chance in the world that they would reach Doctor Atwood. Just a chance, but if they did not take that chance Mrs. Salper would die.

For a long time they tried while the nurse sat quietly in the shadows and Mr. Salper strode up and down, up and down, his face drawn and white, his usually elastic step heavy and dragging.

Again and again went out the call for the Newark station. Minute after minute pa.s.sed, and still Mr. Salper walked up and down uneasily.

"I guess you'll have to give it up----" Herb was beginning when suddenly Bob motioned for silence. The radio was speaking, and he was taking down the message as well as he was able.

"I've got Newark!" the young operator cried excitedly. "Now I'll put in a call for your father, Joe. Where is he staying?"

"At the Robert Treat Hotel."

Once more Bob went to work rather excitedly and even a little clumsily, yet his message went through. In reply he received another, stating that Dr. Atwood had been called by telephone and would be at the sending station inside of fifteen minutes.

"And the best of it is, he is to radiophone," added Bob to Joe. "So you can talk to him direct."

After that the minutes pa.s.sed slowly, both for Mr. Salper and the boys. They thought the end of the wait would never come. But at last the words so eagerly awaited reached them.

There was no mistaking it, even though static interfered and the tuning was not good--Dr. Atwood's voice, cheery, rea.s.suring, helpful.

In his joy at the sound of it, Joe shouted aloud.

"h.e.l.lo, WBZA," came the voice. "If this is Joe talking, give me the high sign, my boy."

During the message Bob had tuned in the right frequency and, with static eliminated one might have thought the speaker was in the same room.

Then there followed a battle with death that the boys would remember as long as they lived. As soon as Doctor Atwood was made to understand the nature of the service asked of him, he became immediately his brisk, professional self.

The nurse, instantly alert herself, gave him a description of the case and it was wonderful as soon as the connection was switched off to hear his kindly voice responding, giving full directions for the care of the patient. He declared that he would be on call all during the night and requested that some one call him every hour--oftener, if it became necessary--to report the progress of the patient.

The nurse hurried off, accompanied by Mr. Salper, and for the rest of the night the boys kept busy, marking a trail between the Salper cottage and the radio station, taking reports from the nurse and carrying directions from Doctor Atwood.

It seemed strange and weird, yet wonderful and soul-stirring, this tending of a patient by a doctor many miles away. Once, during the night, hope almost failed. Mrs. Salper scarcely breathed and lay so still that Edna and Ruth were sure the end had come. They clung to each other sobbing, while Mr. Salper strode up and down, up and down the room as though if he stopped he would die too.

Then came another message from Doctor Atwood. The nurse followed his directions and once more hope came back to the Salper home. The patient rallied, stirred, and for that time at least, the danger was past.

So dawn came at last and Joe and the two younger boys went back to their cottage to try to catch a few hours of sleep. Bob remained at the station, declaring that he felt not at all tired and as soon as the other boys had rested they could come to his relief.

A hard vigil that for Bob. In spite of all he could do, his head would nod and his heavy eyelids close, to be jerked open next moment by the arrival of some one from the Salper home or a message from Doctor Atwood.

News of the struggle had spread all over Mountain Pa.s.s, and people watched with admiration and interest the brave fight that was being made for a woman's life. And sometimes it seemed that, despite all their efforts, the struggle must end in failure.

All that day the battle waged and the next night--the boys taking turns at the radio board, untiring in their determination not to lose.

And Doctor Atwood was as determined as they.

And then, on the morning of the second day came news that the patient had pa.s.sed the much-dreaded crisis and, with the most careful nursing, was sure to recover.

"She'll be all right now," came Doctor Atwood's cheery voice. "It's been a hard pull, but she's past the danger point now. Keep in touch with me, boys, so that, in case of a relapse, I can tell you what to do."

Joe turned to the boys with the light of pride and affection in his eyes.

"That's some dad I've got!" he said.

Later, when the boys walked over to the Salper home to offer congratulations, the girls received them with literally open arms.

"You've saved mother's life!" cried Ruth, with a catch in her voice.

"And we love you for it!" added Edna gratefully. "You just wait till mother knows!"