The price of the gift Danny Dalehouse brought was the lives of the five balloonists who had been sent back to Earth in the return capsule.

The designers at Camp Detrick had made good use of the samples. The two who were dead on arrival were dissected at once. Those were the lucky ones. The other three were studied in vivo. The biggest and strongest of them lasted two weeks.

The Camp Detrick experimenters also had a price to pay, because eight of them came down with the Klongan hives, and one had the severe misfortune to have his skull fill up with antigenic fluid, so that he would never again for the rest of his life stress an experimental subject. Or, indeed, hold a fork by himself. But probably the balloonists who had been his subjects would not have thought that price unfair.

Danny Dalehouse unslung the lightweight carbine from one shoulder and practiced aiming it. Its stock was metal shell, and sintered metal at that; it weighed hardly a kilogram, but half that weight was in high-velocity bullets. It was poor design. He felt sure the recoil would kick him halfway across the sky if he fired it, and anyway, what was the use of high-velocity bullets? What target was there in the Klongan air that needed that sort of impact to destroy it? But the word from Earth brought by the reinforcement party that had been labeled a UN peacekeeping committee was that it must be carried. So he carried it.

He put it back and, somewhat uncomfortably, took Charlie’s gift off the other shoulder. Now, that was more like it. Somebody somewhere had understood what Charlie’s people could do and what they needed in order to protect themselves against predators. It weighed even less than the carbine, and it contained no propellants at all. Its tiny winch could be operated by the claws of a Charlie to tighten a long-lasting elastic cord. Its trigger was sized to fit a balloonist, and what it fired was a cluster of minute needles or, alternatively, a capsule of some sort of fluid. Needles were for airborne predators. The fluid, or so Danny was told, was against creatures like the crabrats, if a balloonist was forced down and needed defense; and it would only incapacitate them without killing.

It would tax all of Dalehouse’s linguistics to convey any part of that to Charlie, but the way to get it done was to begin. He held the crossbow up and sang, carefully attending to the notes he had been taught by the computers at Texas A M. “I have brought you a gift.”

Charlie responded with a burst of song. Dalehouse could understand no more than a few phrases, but clearly it was a message of gratitude and polite inquiry; and anyway, the little tape recorder at his belt was getting it all down for later study.

Danny moved on to the next sentence he had been taught. “You must come with me to find a ha’aye’i. ” That was hard to sing; English does not come with glottal stops, and practicing it for an hour had left Dalehouse’s throat sore. But Charlie seemed to understand, because the song of thanks changed to a thin melody of concern. Danny laughed. “Do not fear,” he sang. “I will be a ha’aye’i to the ha’aye’i. We will destroy them with this gift, and the swarm will no more need to fear.”

Song of confusion, with the words the swarm repeated over and over, not only by Charlie but by all his flock.

The hardest part of all was yet to come. “You must leave the swarm,” sang Dalehouse. “They will be safe. We will return. But now just you and I must fly to seek a ha’aye’i. ”

It took time; but the message ultimately seemed to get across. It was a measure of the balloonist’s trust in his friend from Earth that he was willing to embark on so fearful an adventure with him. The members of the flock never left it by choice. For more than an hour after they had dropped to a lower level and left the flock behind, Charlie’s song was querulous and sad. And no ha’aye’i appeared. They left the Food Bloc camp far behind, drifting down the shore of the sea-lake and then across a neck of it to the vicinity of the Peeps’ tattered colony. For some time Dalehouse had been wondering if the Texas computers had really given him the right words to sing. But then Charlie’s song turned to active fear. They dipped low under a bank of clouds, warm-weather cumuli that looked like female balloonists turned upside down, and from one of them dropped the predatory form of a killer.

Danny was uneasily tempted to slay this first one with his own carbine. It was frightening to see the ha’aye’i stoop toward them. But he wanted to demonstrate his gift to Charlie.

“Watch!” he cried, clumsily grasping the grip that had been designed for balloonist claws. He circled the swelling form of the airshark in the cross-haired sight, designed for balloonist eye patches, feeling the low vibrations of Charlie’s muttered song of terror. At twenty meters he squeezed the trigger.

A dozen tiny metal spikes lashed out at the ha’aye’i, spreading like the cone of fire of a shotgun shell. One was enough. The shark’s bag ripped open with a puff of moisture. The creature screamed once in pain and surprise, and then had no more breath to scream with. It dropped past them, its horrid little face writhing, its claws clutching uselessly toward them, meters away.

A bright trill of surprise from Charlie, and then a roaring paean of triumph. “This is a great good thing, ’Anny ’Alehouse! Will you slay all the ha’aye’i for us?”

“No, not I, Charlie. You will do it for yourself!” And hanging in the air, Danny showed him the clever little crank that worked the elastic cord, the simple breech that the cluster of needles dropped into. For a creature who had never used tools before, Charlie was quick to grasp the operation. Dalehouse had him fire a practice round at a cloud and then watched patiently while the balloonist painfully wound the winch for himself and loaded again.

They were no longer quite alone. Unbidden, the swarm had drifted after them and was floating half a kilometer away, all their eye patches rotated toward them, their distant song sweet and plaintive, like a puppy’s lonely begging to be let in. And down below, the Peeps’ camp was near; Dalehouse could see one or two upturned faces curiously staring at them. Let them look, he thought virtuously; let them see how the Food-Exporting Powers were helping the native races of Klong, if they had so little to do with their time. There were only a handful of them left of the original expedition, and their much-boasted reinforcements showed no signs of arriving.

Reinforcements. Reminded, Dalehouse began the rest of his message for Charlie. “This gift,” he sang, “is yours. But we would ask a gift of you, too.”

“What gift?” sang Charlie politely.

“I do not know words,” sang Danny, “but soon I will show you. My swarm-mates ask you to carry some small things to other places. Some you will drop to the ground. Some you will bring back.” Teaching Charlie how to point the cameras and sound-recording instruments was going to take forever, Dalehouse thought glumly; and how were they ever going to tell him where to drop the clusters of wolftrap sensors and seismic mikes? What seemed so simple on Earth was something else entirely on Klong -

“Beware, beware!” sang the distant, frantic voices of the swarm.

Tardily Danny looked around. The ha’aye’i’s rush caught them unaware. It came from behind and below, where Dalehouse had not thought to look. And Charlie, fondling his new toy and trying to understand what Dalehouse wanted of him, had been careless.

If it had not been for the distant shrieking of the swarm, the creature might have had them both. But Charlie spun faster than Dalehouse, and before Danny could unlimber his carbine the balloonist had shown how well he had learned his lesson by killing the killer. Either of them could have reached out and caught the long, wicked claws of the ha’aye’i as it fell past them; it was that close.