“The lights are being carried,” Liddy said suddenly. “They are some sort of oblong balls, all filled with light.”

“Bioluminescent,” Bony added. To him they were still shapeless blobs. “That’s what you would expect in marine organisms, some form of phosphorescence or bioluminescence. You wouldn’t expect ordinary combustion.”

“Stuff your combustion.” Indigo sounded frantic. “I don’t want idiot science lectures. Carried by what , Liddy?”

“I can’t tell yet. But in another minute or two we can get a closer look—”

“The scopes!” Bony shouted the words, while he groaned inside at his own mental inadequacy. He had been peering hopelessly and unthinkingly into the darkness like Neanderthal man trying to see outside his cave, while the Mood’s sophisticated imaging sensors and image intensifiers sat unused beside him. He fumbled his way to the console, turned on an internal light, and pulled up a display connected to the scopes. A few of them would certainly not work — thermal infrared sensors relied on radiation, not physical contact with the sensors — but visible wavelengths should be fine.

Another half minute when he seemed to be all thumbs, and then he had it. The screen showed a patch of lights at its center. He zoomed in.

And there they were. He had half known it, even before he thought of using the scopes. Fourteen bubble creatures — now he could count them, easily — were drifting toward the ship along the seabed. Each one floated in front of it a giant light, pear-shaped but the size of a watermelon. With that illumination Bony could make out every detail of their bodies.

The ball-like heads sat on rounded iridescent trunks that quivered when the creatures moved, as though the whole animal was boneless and made of soft jelly. Nothing in the head resembled a nose or mouth, unless it was the wide horizontal slit that sat close to the top of the rounded body. Above the head, connected to it by a pair of delicate-looking fringed stalks or antennae, hovered two green spheres that were probably eyes. If so they were separately controlled, turning independently and apparently randomly to point in different directions. The watermelon-pear light was carried easily by four string-of-bubble arms or tentacles, and four more waving limbs attached to the bottom of the globular body carried it easily over the uneven ocean floor.

The whole added up to such an appearance of fragility and vulnerability that Bony felt reassured. The creatures shown by the scope seemed as soft and harmless as children’s toys. But so, he reminded himself, did a Portuguese man-of-war, with its agonizing sting.

Liddy Morse and Friday Indigo had moved away from the port to stand next to Bony, staring at the display.

“Son of a bitch,” Indigo said softly. “They’re real. You didn’t make them up after all.”

“They’re real all right.” Bony had the computer hooked in to the scope circuit, analyzing the movement of the creatures on the display. He glanced at its output. “Real, heading right for us, and unless they decide to stop they’ll be here in seven minutes.”

“What do we do?”

Apparently Indigo had decided that Bony, science lectures and all, was not such an idiot. Bony thought for a moment. “If they’re as soft as they look, there’s no way that they can damage the hull. But I’ve been wrong so often today I wouldn’t put money on it. I suppose we could all put space-suits on. But I doubt if it’s worth it. If they can break into the hull, the suits won’t hold them for a minute.”

Indigo nodded. “No suits, then. So what do we do?”

The same question again, and a very reasonable one. But Bony was out of ideas. He had been exhausted, even before he and Liddy arrived back aboard the ship. Now he felt giddy with fatigue, and his brain had already gone on strike. “I guess” — he looked apologetically at the other two — “I guess we wait.”

Seven minutes.

The sea-creatures steadily came closer. The tension in the cabin grew until it was thick enough to choke them. No one had anything to say.

Six and a half minutes.

Bony decided that seven minutes would hardly feel longer if you were being operated on without anesthetics by a sadistic torturer. Purely for something to do, he asked the ship’s computer what a planet would be like if it had the same gravity as Earth’s moon and was the size of Earth. It asked him a bunch of foolish questions about density distributions, none of which he could answer. He told it to make any default assumptions it liked, and stop bothering him.

The answer came quickly, but it was not very informative. If a world had the same size and internal mass distribution as the Earth, then if its surface gravity was equal to the Moon’s mean surface gravity, its average density would be 0.91.

Less than one. According to the computer, the average density was less than that of ordinary water. But the whole ocean of Limbo was salty heavy water, with a density fifteen percent more than ordinary water. There was no way that Limbo ought to possess an ocean at all. At that planetary density, all liquid water should have sunk below the surface.

Bony stared at the offending number. Nothing about Limbo made sense. The ridiculously low density. The heavy-water sea. The blue giant star, too young to allow life to develop on a planet around it. The Link access point, in water where no Link access could be. And if there were such a Link point, how had they been able to transfer to it when the ship’s automatic protection system forbade transfer with substantial matter present? Limbo simply became stranger and stranger with every passing hour.

But maybe it was about to get stranger yet. In the darkened cabin, Liddy said softly, “They’re here.”

It was not necessary to use the imaging sensors and the enhancers to know that. They could see light shining in through the ports. The ring of sensors on the Mood Indigo stood about four meters above the seabed, and they gave an excellent view of the scene below. Fourteen bubble-creatures, each with its light, had drifted to surround the ship in a rough circle. As Bony watched, one of them left the circle and floated in toward the base of the vessel, beyond the imaged area. A soft thump vibrated through the hull. It sounded more exploratory than violent, but Indigo said nervously, “They’re attacking the ship. What do we do now?”

“That doesn’t seem like an attack. No, don’t!” Bony spoke to Liddy, who was about to go over to the port. “Stay here, where we can see them with the image system and they can’t see us. I don’t think they have good night vision, because they’re carrying lights. But if you get close to the port they may see reflected light from your face. Keep your voice down, too. If they can’t see or hear us they may go away.”

“It’s back in the circle,” Indigo said. “The one who banged on the ship, I mean. They’re all there now. Uh-oh. What are they doing?”

The giant glowing pear-shapes were dimmer, and the scene provided by the ship’s imaging sensors was fading steadily to a uniform gray.

“I don’t know how they’re doing it, but the lights they’re carrying are going out.” Bony clicked the image sensitivity range to a different setting, and the scene outside again became visible, now in black and white. “Look at them. They seem to be settling down. I think the Limbics are going to sleep.”

“The who?” Friday Indigo stared. “Where the hell did you get that from?”

“We need a name for them, and they live on Limbo. I think they’re probably intelligent, seeing how they use portable lights to see at night.”

The creatures no longer stood above the seabed on their bubble strings of tentacles. Instead, the rounded end of the body had settled comfortably down onto the sea floor, where the array of pikes had been crumbled to dust by the arrival of the Mood Indigo. At the upper end of the body, the antennae with their green sphere eyes drooped down to sit on each side of the soap-bubble head. Each had placed its light neatly on the sea floor, with the wide end of the pear facing down.