Not at all to the discredit of the moving picture boys is it to be considered when it is recorded that, following this question on the part of Mr. Hadley, they looked sharply at one another.

"A call to battle!" murmured Joe.

"Actual fighting?" added his chum wonderingly.

"Perhaps I'd better explain a bit," went on the film producer. "Most unexpectedly there has come to me an opportunity to get some exceptional pictures. I need resourceful, nervy operators to act as camera men, and it is only paying you two a deserved compliment when I say I at once thought of you."

"Thank you," murmured Blake.

"No thanks necessary," responded Mr. Hadley.

"So now I am ready to put my offer into words. In brief, it is——"

At that moment back of the farmhouse (which was partly in ruins, for the fire had been a real one) a loud explosion sounded. This was followed by shouts and yells.

"Somebody's hurt!" cried Mr. Hadley, and he set off on a run toward the scene, followed by Blake and Joe.

And while they are investigating what had happened, advantage will be taken of the opportunity to tell new readers something of the former books in this series, so they may feel better acquainted with the two young men who are to pose as "heroes," as it is conventionally termed, though, in truth, Joe and Blake would resent that word.

"The Moving Picture Boys" is the title of the first volume of the series, and in that the readers were introduced to Blake Stewart and Joe Duncan while they were working on adjoining farms. A moving picture company came to the fields to make certain scenes and, eventually, the two young men made the acquaintance of the manager, Mr. Hadley.

Blake and Joe were eager to get into the film business, and their wish was gratified. They went to New York, learned the ins and outs of the making of "shifting scenes," as the Scotchman called them, and they had many adventures. The boys became favorites with the picture players, among whom were the gloomy C. C., Miss Shay, Miss Lee, Harris Levinberg and Henry Robertson. Others were added from time to time, sometimes many extra men and women being engaged, in, for instance, scenes like these of "The Dividing Line."

Following their adventures in New York, which were varied and strenuous, the moving picture boys went out West, taking scenes among the cowboys and Indians.

Later they moved on, with the theatrical company, to the coast, where they filmed a realistic picture of a wreck. In the jungle was where we next met Blake and Joe, and they were in dire peril more than once, photographing wild animals, though the dangers there were surpassed when they went to Earthquake Land, as they called it. The details of their happenings there will be found in the fifth volume of the series.

Perilous days on the Mississippi followed, when Blake and Joe took pictures of the flood, and later they were sent to Panama to make views of the digging of the big canal.

Mr. Hadley was a producer who was always eager for new thrills and effects. And when he thought he had exhausted those to be secured on the earth, he took to the ocean. And in "The Moving Picture Boys Under the Sea," the book that immediately precedes the present volume, will be found set down what happened to Blake and Joe when, in a submarine, they took views beneath the surface.They had not long been home from their experiences with the perils of the deep when they were engaged to make views for "The Dividing Line," with its battle pictures, more or less real.

"What's the matter? What happened? Is any one hurt?" cried Mr. Hadley, as he ran toward the scene of the explosion, followed by Blake and Joe. They could see, by a large cloud of smoke, that something extraordinary had occurred. The figures of several men could be noted running about.

"Is anybody hurt?" demanded the producer again, as he and the two boys reached the place. "I'll send the ambulance, if there is." For when a film battle takes place men are often wounded by accident, and it is necessary to maintain a real hospital on the scene.

"I don't believe any one's hurt," remarked Mr. Robertson, who did juvenile leads.

"Unless it might be C. C.," remarked Mr. Levinberg, who was usually cast as a villain. "And small loss if he was laid up for a week or so. We'd be more cheerful if he were."

"Is C. C. hurt?" asked Joe.

"No; but I guess he's pretty badly scared," answered Mr. Robertson. "After this I guess he'll have more respect for a smoke bomb."

"Was that what exploded?" asked Mr. Hadley.

"Yes," replied the "villain." He pointed to Mr. C. C. Piper walking along in the midst of a group of soldiers. "It happened this way: We were talking about the battle scene, and C. C. kept saying it would be a failure when projected because the smoke bombs were not timed right. He said they should explode closer to the firing line, and some of the men who handled them said they held them as long as they dared before throwing them.

"Old C. C. sneered at this, and said he could hold a smoke bomb until the fuse was burned down out of sight, and then throw it and get better results. So they dared him to try it."

"Well?" asked Mr. Hadley, as the actor paused.

"Well, C. C. did it. He held the smoke bomb, all right, but he didn't throw it soon enough, and, as a result, it exploded almost in his face. Lucky it's only made of heavy paper and not very powerful powder, so he was only knocked down and scorched a little. But I guess he'll have more respect for smoke bombs after this."

"Foolish fellow!" remarked Mr. Hadley. "He never will listen to reason. I hope he isn't badly hurt."

"It's only his feelings, mostly," declared the juvenile actor.

Mr. Piper, otherwise called C. C., came limping along toward the producer and the moving picture boys.

"Mr. Hadley, you may have my resignation, effective at once!" cried the tragedian.

"Oh, don't say that, Mr. Piper. You're not hurt——"

"Well, it isn't any thanks to one of your men that I'm not. I offered to show them how to throw a smoke bomb, and they gave me one with an extra short fuse. It went off almost in my face. If my looks aren't ruined my nerves are, and——"

"No danger of your nerve being gone," murmured Blake, nudging his chum.

"I should say not!"

"Anyhow, I resign!" declared C.C. savagely.

But, as he did this on the average of twice a week, it had become so now that no one paid any attention to him. Mr. Hadley, seeing that he was in no danger and hardly even painfully scorched, no longer worried about the gloomy comedian.

"And now to get back to what we were talking about before that interruption came," said Mr. Hadley to the moving picture boys. "Do you think you'd like to tackle the job?"

"What is it?" asked Blake.

"Give us an idea," added his chum.

"Well, it isn't going to be any easy work," went on the producer. "And I might as well tell you, first as last, that it will be positively dangerous on all sides."

"Like anything we've done before?" Blake wanted to know.

"Not exactly. Earthquake Land is as near like it as anything that occurs to me. In short, how would you like to go to Europe?"

"To the war?" cried Joe.

"Yes; but to take films, not prisoners!"

"Great!" cried Blake. "That suits me, all right!"

"The same here!" agreed Joe instantly. "Tell us more about it!"

"I will in a few days," promised the producer. "I have several details to arrange. Meanwhile, I have a little commission for you along the same line, but it's right around here—or, rather, down in Wrightstown, New Jersey, at one of the army camps.

"I can tell you this much: If you go to Europe, it will be as special agents of Uncle Sam, making films for the use of the army. You will be commissioned, if my plans work out, though you will be non-combatants. The war department wants reliable films, and they asked me to get some for them. I at once thought of you two as the best camera men I could pick out. I also have a contract for getting some films here of army encampment scenes, and you can do these while I'm waiting to perfect my other arrangements, if you like."

"Down at Wrightstown, is it?" cried Joe. "Well, I guess we can take that in. How about it, Blake?"

"Sure we can. That is, if you're through with us on this serial."

"Yes. The most important scenes of that are made now, and some of my other camera men will do for what is left. So if you want to go to the Jersey camp I'll get your papers ready."

"We'll go," decided Blake.

Two days later, during which they wondered at and discussed the possibilities of making films on the battle fronts of Europe, the two youths were in Wrightstown.

One incident occurred while they were at work there that had a considerable bearing on what afterward happened to them. This was after Joe and Blake had finished making a fine set of films, showing the drilling of Uncle Sam's new soldiers, the views to be used to encourage enlistments about the country.

"These are some of the best views we've taken yet in this particular line," observed Joe to Blake, as they sent the boxed reels to New York by one of their helpers to be developed.

"Yes, I think so myself. Of course, they're peaceful, compared to what we may take in France, but——"

He was interrupted by the unexpected return of Charles Anderson, nicknamed "Macaroni," their chief helper, who hurriedly entered the tent assigned to the two boys.

"What's the trouble, Mac?" asked Joe, that being the shortened form of the nickname. "You look worried."

"And so would you, Joe, if you'd had an accident like mine!"

"An accident?" cried Blake, in some alarm.

"Yes! At least, he said it was an accident!"

"Who said so?"

"That Frenchman!"

"What accident was it?"

"Why, he ran into me with his auto, and the army films are all spoiled—light-struck!"

"Whew!" whistled Blake, and Joe despairingly banged his fist against his camera.