"He is out, too," said von Liegnitz. "He also is on duty."

Mike the Angel lifted an inquisitive eyebrow. "Something busted? Why should the Maintenance Officer be on duty right now?"

"He is maintaining," said von Liegnitz with deliberate dignity, "peace and order around here. He is now performing the duty of Answerman-in-Chief. He"s very good at it."

Mike grinned. "Snook.u.ms?"

Von Liegnitz scooped the cards off the table and began shuffling them.

"Exactly. As long as Snook.u.ms gets his questions answered, he keeps himself busy. Our young boot ensign has been a.s.signed to the duty of keeping that mechanical Peeping Tom out of our hair for an hour. By then, it will be lunch time." He cleared his throat. "We still need a fourth."

"If you ask me," said Lieutenant Keku, "we need a fifth. Let"s play poker instead."

Jakob von Liegnitz nodded and offered the cards for a cut.

"Deal "em," said Mike the Angel.

A few minutes less than an hour later, Ensign Vaneski slid open the door to the wardroom and was greeted by a triune chorus of h.e.l.los.

"Sirs," said Vaneski with pseudo formality, "I have done my duty, exhausting as it was. I demand satisfaction."

Lieutenant Keku, upon seeing Mike the Angel dealt a second eight, flipped over his up cards and folded.

"Satisfaction?" he asked the ensign.

Vaneski nodded. "One hand of showdown for five clams. I have been playing encyclopedia for that hunk of animated machinery for an hour.

That"s above and beyond the call of duty."

"Raise a half," said Mike the Angel.

"Call," said von Liegnitz.

"Three eights," said Mike, flipping his hole card.

Von Liegnitz shrugged, folded his cards, and watched solemnly while Mike pulled in the pot.

"Vaneski wants to play showdown for a fiver," said Keku.

Mike the Angel frowned at the ensign for a moment, then relaxed and nodded. "Not my game," he said, "but if the Answerman wants a chance to catch up, it"s okay with me."

The four men each tossed a five spot into the center of the table and then cut for deal. Mike got it and started dealing--five cards, face up, for the pot.

When three cards apiece had been dealt, young Vaneski was ahead with a king high. On the fourth round he grinned when he got a second king and Mike dealt himself an ace.

On the fifth round Vaneski got a three, and his face froze as Mike dealt himself a second ace.

Mike reached for the twenty.

"You deal yourself a mean hand, Commander," said Vaneski evenly.

Mike glanced at him sharply, but there was only a wry grin on the young ensign"s face.

"Luck of the idiot," said Mike as he pocketed the twenty. "It"s time for lunch."

"Next time," said Keku firmly, "I"ll take the Answerman watch, Mike. You and this kraut are too lucky for me."

"If I lose any more to the Angel," von Liegnitz said calmly, "I will be a very sour kraut. But right now, I"m quite hungry."

Mike prowled around the Power Section that afternoon with a worry nagging at the back of his mind. He couldn"t exactly put his finger on what was bothering him, and he finally put it down to just plain nerves.

And then he began to feel something--physically.

Within thirty seconds after it began, long before most of the others had noticed it, Mike the Angel recognized it for what it was. Half a minute after that, everyone aboard could feel it.

A two-cycle-per-second beat note is inaudible to the human ear. If the human tympanum can"t wiggle any faster than that, the auditory nerves refuse to transmit the message. The wiggle has to be three or four octaves above that before the nerves will have anything to do with it.

But if the beat note has enough energy in it, a man doesn"t have to hear it--he can _feel_ it.

The bugs weren"t all out of the _Brainchild_, by any means, and the men knew it. She had taken a devil of a strain on the take-off, and something was about due to weaken.

It was the external field around the hull that had decided to goof off this time. It developed a nice, unpleasant two-cycle throb that threatened to shake the ship apart. It built up rapidly and then leveled off, giving everyone aboard the feeling that his lunch and his stomach would soon part company.

The crew was used to it. They"d been on shakedown cruises before, and they knew that on an interstellar vessel the word "shakedown" can have a very literal meaning. The beat note wasn"t dangerous, but it wasn"t pleasant, either.

Within five minutes everybody aboard had the galloping collywobbles and the twittering jitters.

Mike and his power crew all knew what to do. They took their stations and started to work. They had barely started when Captain Quill"s voice came over the intercom.

"Power Section, this is the bridge. How long before we stop this beat note?"

"No way of telling, sir," said Mike, without taking his eyes off the meter bank. "Check A-77," he muttered in an aside to Multhaus.

"Can you give me a prognosis?" persisted Quill.

Mike frowned. This wasn"t like Black Bart. He knew what the prognosis was as well as Mike did. "Actually, sir, there"s no way of knowing. The old _Gainsway_ shook like this for eight days before they spotted the tubes that were causing a four-cycle beat."

"Why can"t we spot it right off?" Quill asked.

Mike got it then. Fitzhugh was listening in. Quill wanted Mike the Angel to substantiate his own statements to the roboticist.

"There are sixteen generator tubes in the hull--two at each end of the four diagonals of an imaginary cube surrounding the ship. At least two of them are out of phase; that means that every one of them may have to be balanced against every other one, and that would make a hundred and twenty checks. It will take ten minutes if we hit it lucky and find the bad tubes in the first two tries, and about twenty hours if we hit on the last try.

"That, of course, is presuming that there are only two out. If there are three...." He let it hang.

Mike grinned as Dr. Morris Fitzhugh"s voice came over the intercom, confirming his diagnosis of the situation.

"Isn"t there any other way?" asked Fitzhugh worriedly. "Can"t we stop the ship and check them, so that we won"t be subjected to this?"

""Fraid not," answered Mike. "In the first place, cutting the external field would be dangerous, if not deadly. The abrupt deceleration wouldn"t be good for us, even with the internal field operating. In the second place, we couldn"t check the field tubes if they weren"t operating. You can"t tell a bad tube just by looking at it. They"d still have to be balanced against each other, and that would take the same amount of time as it is going to take anyway, and with the same effects on the ship. I"m sorry, but we"ll just have to put up with it."