But when the Kwembly stopped, it was on Beetchermarlf’s initiative. It was a minor thing, or seemed to be; the soil ahead seemed a little darker, with a very sharp boundary between it and the surface under the cruiser. The line was not noticeable on the vision screen, but the Mesklinites spotted it simultaneously and, without words, agreed that close examination was in order. Beetchermarlf called the station to inform the human beings and his captain that he and Takoorch would be going outside for a time, and described the situation. Easy, translating the message, was promptly begged by two planetologists to persuade the Mesklinites to bring samples aboard. She assumed that even Aucoin would hardly object under the circumstances, and agreed to ask them when she called back with Dondragmer’s clearance.

The captain, this time, approved the sortie, suggesting only that it be preceded by a careful look around from the bridge with the aid of the spotlights. This proved useful. A hundred yards ahead, not too far out of the range of the running lights, a small stream ran across their path and emptied into the river. Sweeping the light to starboard, this tributary could be seen arcing around parallel to the cruiser’s path from the north, then reversing its curve somewhat astern of the big vehicle and disappearing to the northwest. The Kwembly was on a peninsula some two hundred yards wide and not quite as long, bounded on the east — left — by the main river she had been following and on the other sides by the small tributary. It seemed likely to Mesklinites and human beings alike that the change in soil color which had caught the helmsmen’s attention was caused by wetting from the smaller stream, but no one was sure enough of it to cancel the proposed trip outside. Aucoin was not present.

Outside, even with the aid of extra lights, the line of demarcation between the two kinds of soil was much less visible than before. Eye distance, Beetchermarlf judged, was the main cause. The crew scraped up and packaged samples of material from both sides of the line; then they went on to the stream itself This proved to be a swift-running but shallow brook three or four body-lengths in width, its level an inch or two below the soil through which it was cutting its way. After a brief consultation, the two Mesklinites began to follow it away from the river. They had no way of telling its composition, but a bottle of its contents was secured for later testing.

By the time they reached the spot where it was curving away, even the Mesklinites could see that the stream had not been in existence very long. It was eating with visible speed into its banks, washing the sediment on toward the main river. Now that they were on the outside of its curve, the undercutting of the near bank could be seen and even felt; Beetchermarlf, standing at the edge, felt it crumble suddenly away under him and found himself in the stream.

It was only an inch or so deep, so he took advantage of the occasion to take another sample from its bottom before climbing out. They decided to continue upstream for another ten minutes or so, with Beetchermarlf wading and Takoorch on the bank. Before the time was up they had actually found the source of the watercourse. It was a spring, not half a mile from the Kwembly, roiling violently in the center of its basin where an underground source fed it. Beetchermarlf, investigating the middle, was knocked from his feet and carried half a body length by the upward current.

There was nothing in particular to do; they had no camera equipment, no one had seriously suggested that they bring the vision set with them, and there was nothing obvious to be gained by collecting more samples. They returned to the Kwembly to give a verbal description of what they had found.

Even the scientists agreed that the best step now was to get the samples back to the camp where Borndender and his fellows could do something useful with them. The helmsmen eased their cruiser into motion once more.

It approached the stream and nosed through it; the mattress took up the slight dip as the trucks crossed the bottom of the widening valley, and nothing could be felt on the bridge.

Not for another eight seconds.

The hull was rather more than halfway across the little brook when the distinction between solid and liquid began to blur. A slight lurch could be felt on the bridge; it showed on the screen far above as a tiny upward jerk of the few outside features visible.

Forward motion stopped almost instantly, though the drivers kept churning. They could accomplish nothing when completely immersed in slimy mud, which the surface had so suddenly become. There was neither support nor traction. The Kwembly settled until the trucks were buried; settled until the mattress was nearly out of sight; settled almost, but not quite, to the level where she would have been literally floating in the semi-liquid muck. She was stopped by two of the rock outcrops, one of which caught her under the stern just aft of the mattress, and the other on the starboard side some ten feet forward of the main lock. There was an ugly scraping sound as the cruiser’s hull canted forward and to port, and then came to rest.

And this time, as Beetchermarlf’s sense of smell warned him only too clearly, the hull had failed somewhere. Oxygen was leaking in.

“It boils down to this,” Aucoin said from the head of the table. “We have the choice of sending down the barge, or not. If we don’t, the Kwembly and the two Mesklinites aboard her are lost, and Dondragmer and the rest of her crew are out of action until a rescue cruiser such as the Kalliff can reach them from the Settlement. Unfortunately, if we do try to land the barge there’s a good chance that it won’t help. We don’t know why the ground gave under the Kwembly, and have no assurance that the same thing won’t happen anywhere else in the vicinity. Losing the barge would be awkward. Even if we first landed near Dondragmer’s camp and transferred him and his crew to the cruiser, we might lose the barge and there is no assurance that the crew could repair the Kwembly. Beetchermarlf’s report makes me doubt it. He says he has found and sealed the major leaks, but he’s still getting oxygen inside the hull from time to time. Several of his life-support tanks have been poisoned by it. So far he has been able to clean them out each time and restock them from the others, but he can’t keep going forever unless he stops the last of these leaks. Also, neither he nor anyone else has made any concrete suggestion for getting that cruiser loose from the muck or whatever it’s stuck in.

“There is another good argument against landing the barge. If we use remote, live control, there is the sixty-second reaction lag, which would make handling anywhere near the ground really impossible. It would be possible to program its computer to handle a landing, but the risks of that were proved the hard way the first time anyone landed away from Earth. You might as well give the Mesklinites a quick lesson in flying the thing for themselves!”

“Don’t try to make that last sound too silly, Alan,” Easy pointed out gently. “The Kwembly is merely the first of the cruisers to get into what looks like final trouble. Dhrawn is a very big world, with very little known about it, and I suspect we’re going to run out of land-cruisers for rescue or any other purpose sooner or later. Also, even I know that the barge controls are computer-coupled, with push-the-way-you-want-to-go operators. I admit that even so, the chances are ten to one or worse that anyone trying a ground-to-ground flight with that machine on Dhrawn without previous experience would kill himself, but do Beetchermarlf and Takoorch have even that much chance of survival on any other basis?”