“But I thought you suspected us of setting fire to the forest,” said Charley.

“I never said so,” replied Mr. Marlin.  “I merely asked you if you had started the fire.”

“It’s pretty much the same thing,” said Charley.

“Not at all, young man.  Not at all.  I did not really suspect you.  But I saw there was a possibility that you might have done just what I suggested.  I wanted to see what you would do when I suggested that you were the culprit.  I could have told if you had lied to me.”

“How?” demanded Charley.

“Never mind now,” smiled the forester.  “But while we are on this subject, I want to say this to you:  when you are trying to solve a crime, you must forget your prejudices.  You must look at the facts and not at the people concerned.  You must take the attitude that anybody may be guilty until he is proved innocent.  In short, you must be ready to suspect anybody.  You must not assume, for instance, that because I am the forester I would not set the forest afire, or because my rangers are connected with the Forest Service they would never start a fire.”

Charley looked almost startled.  “Why, it would be the worst sort of crime for a forest protector to set a fire in the woods,” he cried.

“Of course it would,” replied the forester.  “But in this world almost everybody acts according to his own interests or his own passions.  If a man could earn more money by setting fires than by preventing them, there are many men who would take the chance.  Or a man might set fire to the forest to be revenged on somebody—­possibly on me; for a forester can hardly avoid making some enemies.”

The forester paused.  “Somebody has three times set this part of the forest afire,” he continued after a moment.  “We have no clue as to who did it.  So it is our business to suspect anybody and everybody that circumstances may point to.  But that doesn’t mean we must condemn a person merely because circumstances point to him.  We must study the facts and either condemn or acquit him according to the facts.  I say this to you because you have probably had little or no experience in tracing crime and, like most young folks, are prone to trust people too far.”

Charley’s face was very serious.  He had not thought of detective work as a possible part of his duties.

“Don’t take what I say too seriously,” laughed the forester, when he noticed Charley’s expression.  “You will really have very little of this sort of thing to do.  Most fires come through the carelessness of campers.  To warn them to be careful, to try to put out fires as soon as you discover them and notify me if you fail, will be about all you will ordinarily have to do.  The chief forest fire-warden will attend to investigating fires.  But in this case, I especially want to know how this fire started.  Sometimes boys, if they are shrewd enough, make the best of all agents for watching folks.  People don’t take boys seriously, and will often do or say incriminating things before boys that they would not dream of doing in the presence of grown men.  If you keep your eyes and ears open and your mouth shut, you may be very useful.  And the less you appear to know, the more useful you will be.”