“Guess he didn’t like that little chum we left on for him,” Bud said with a chuckle.

“Let’s leave him where he is,” Tom agreed.

The two boys went back to the adjoining apartment and were soon asleep again.  Several hours later they were rudely awakened by a loud crash of glass and a heavy thud.

“Something’s happening to Exman!” Tom cried.

With Bud at his heels, the young inventor dashed into the laboratory.

CHAPTER XII

EXMAN TAKES ORDERS

A strange sight greeted Tom’s and Bud’s eyes.  In the first rays of sunlight, the space robot was moving back and forth about the laboratory in wild zigzag darts and lunges.

As he rolled toward a bench or other object, the brain energy seemed to send out invisible waves that knocked things over!  Already the floor was strewn with toppled lab stools, books, and broken test tubes.  The heavy thud had apparently been caused by a falling file cabinet.

“Stop him!” Bud yelped.

Exman was heading straight for a plate-glass window!  Reaching from floor to ceiling, the glass formed one entire wall of the laboratory.

“Oh, no!” Tom tensed, realizing that it was hopeless to try to stop Exman in time.

But an instant later, the rolling robot stopped of its own accord, as if registering the fact that its energy waves were now striking a fragile surface.  The thick pane of glass vibrated in its frame.

“Good grief!” Tom wiped his brow.  “Let’s corral that thing before he wrecks the whole lab!”

Exman was already rolling off on a new tack.  The two boys managed to grab him before more harm was done.  The brain energy in its container seemed to calm under their touch.

“What in the name of space science triggered it off?” Bud wondered out loud.

“Time.  It must have reacted to the passage of time,” Tom conjectured.  “I suppose it just decided to explore this place.”  He added a bit nervously, “The sooner we can communicate with this energy, the better!”

“But how?” Bud asked.

Tom’s brow furrowed.  “Say, I wonder if Exman might understand a direct order?”

Tom backed a few paces away from the space robot, then said in a loud, clear voice, “Come here!”

Exman remained fixed to its spot.

“Move right!” No response.  “Move left!” Still no response.

“Guess you’re not getting through, skipper,” Bud commented with a grin.

“No,” Tom agreed.  “I can’t predict what kind of energy this brain will respond to.  Being only energy, it must respond to other energy and sound is our form of energy.  The problem is the same as with radio waves, which are also energy.  We must figure out how we can vary the energy, so it can transmit information to Exman.”

“What do we try?” Bud asked.  “Or is it hopeless?”