was possible to estimate the approximatelocation of either sun or Earth at a given time, but calculationsinvolved in working out too many possibilities on different Earth-daysof the Lunar-day made the Earth's shadow-casting the likeliestprospect. Neither location was particularly exact, and probably LairdMartin had expected his directions to be gone into under lessharrowing circumstances than those in which Denver now found himself.With time for trial and error one could eventually locate the place.

  But Denver was hurried. He trod upon one of the markings while hestill sought the elusive shadow apex.

  After that, it was a grim race to follow the markings to the oldmines, and to get under cover behind defensible barricades in time torepel invasion.

  They played a nerve-wracking game of hare and hounds in tricky floodsof Earthlight, upon slopes and spills of broken rock, amid a goblin'sgarden of towering jagged spires. It was tense work over the badgoing, and the light was both distorted and insufficient. In shadow,they groped blindly from arrow to arrow. In the patches of Earthglare,they fled at awkward, desperate speed.

  Life and death were the stakes. Life, or a fighting chance to defendlife, possible wealth from the ancient workings, made a glitteringgoal ahead. And ever the gray hounds snapped at their heels, withdeath in some ugly guise the penalty for losing the game.

  Charley was ecstatic. He gamboled and capered, he zoomed andzigzagged, he essayed quick, climbing spirals and almost came togrief among the tangled pinnacles on the ridge of the hogback. Heswooped downward again in a series of shallow, easy glides and beganthe performance all over again. It was a game for him, too. But a gamein which he tried only to astound himself, with swift, dizzy miraclesof magnetic movement.

  Charley enjoyed himself hugely. He was with the two people he likedmost. He was having a spirited game among interlaced shadows andsudden, substantial obstacles of rock. He nuzzled the fleeing pairplayfully, and followed them after his own lazy and intricate andincredibly whimsical fashion. His private mode of locomotion was notbounded by the possibilities involved in feet and tiring legs. Hescampered and had fun.

  It was not fun for Tod Denver and Darbor. The girl's strength wasfailing. She lagged, and Denver slowed his pace to support hertottering progress.

  Without warning, the mine entrance loomed before them. It was old andcrumbly with a thermal erosion resembling decay.

  It was high and narrow and forbiddingly dark.

  Tod Denver had brought portable radilumes, which were needed at once.Inside the portals was no light at all. Thick, tangible dark blockedthe passage. It swallowed light.

  Just inside, the mine gallery was too wide for easy defense. Furtherback, there was a narrowing.

  * * * * *

  Denver seized on the possibilities for barricading and set to work,despite numbed and weary muscles. Walking on the Moon is tiring formuscles acquired on worlds of greater gravity. He was near exhaustion,but the stimulus of fear is strong. He worked like a maniac, haulingmaterials for blockade, carrying the smaller ingredients and rollingor dragging the heavier. A brief interval of rest brought Darbor tohis side. She worked with him and helped with the heavier items.Fortunately, the faint gravity eased their task, speeded it.

  For pursuit had not lagged. Their trail had been found and followed.

  From behind his barricade, Denver picked off the first two hired thugsof the advance guard as they toiled upward, too eagerly impatient forcaution. A network of hastily-aimed beams of heat licked up fromseveral angles of the slope, but none touched the barricade. Theslope, which flattened just outside the entrance made exact shootingdifficult, made a direct hit on the barricade almost impossible,unless one stood practically inside the carved entrance-way. Denverinched to the door and fired.

  The battle was tedious, involved, but a stalemate. Lying on his belly,Denver wormed as close as he dared to the break of slope outside thedoor. There, he fired snap shots at everything that moved on theslopes. Everything that moved on the slopes made a point of returningthe gesture. Some shots came from places he had seen no movement.

  It went on for a long time. It was pointless, wanton waste ofheat-blaster ammunition. But it satisfied some primal urge in thehuman male without solving anything.

  Until Darbor joined him, Denver did not waste thought upon thefutilities of the situation. Her presence terrified him, and he urgedher back inside. She was stubborn, but complied when he dragged herback with him.

  "Now stay inside, you fool," she muttered, her voice barely a whisperin his communication amplifier.

  "You stay inside," he commanded with rough tenderness. They bothstayed inside, crouched together behind the barricade.

  "I think I got three of them," he told her. "There seemed to be eightat first. Some went back to the ship. For more men or supplies, Idon't know. I don't like this."

  "Relax," she suggested. "You've done all you can."

  "I guess it's back to your gilded cage for you, baby," he said. "Mymoney didn't last."

  "Sometimes you behave like a mad dog," she observed. "I'm not sure Ilike you. You enjoyed that butchery out there. You hated to comeinside. What did it prove? There are too many of them. They'll killus, eventually. Or starve us out. Have you any bright ideas?"

  Denver was silent. None of his ideas were very bright. He was at theend of his rope. He had tied a knot in it and hung on. But the ropeseemed very short and very insecure.

  "Hang on, I guess. Just hang on and wait. They may try a rush. If theydo I'll bathe the entrance in a full load from my blaster. If theydon't rush, we sit it out. Sit and wait for a miracle. It won't happenbut we can hope."

  Darbor tried to hug the darkness around her. She was a Martian,tough-minded she hoped. It would be nasty, either way. But death wasnot pleasant. She must try to be strong and face whatever came. Sheshrugged and resigned herself.

  "When the time comes I'll try to think of something touching andsignificant to say," she promised.

  "You hold the fort," Denver told her. "And don't hesitate to shoot ifyou have to. There's a chance to wipe them out if they try to force inall at once. They won't, but--"

  "Where are you going? For a walk?"

  "Have to see a man about a dog. There may be a back entrance. I doubtit, since Martian workings on the Moon were never very deep. But I'dlike a look at the jackpot. Do you mind?"

  Darbor sighed. "Not if you hurry back."

  Deep inside the long gallery was a huge, vaulted chamber. Here, Denverfound what he sought. There was no back entrance. The mine was a trapthat had closed on him and Darbor.

  Old Martian workings, yes. But whatever the Martians had sought anddelved from the mooncrust was gone. Layered veins had petered out,were exhausted, empty. Some glittering, crystalline smears remained inthe crevices but the crystals were dull and life-less. Denver bentclose, sensed familiarity. The substance was not unknown. He wetted afinger and probed with it, rubbed again and tested for taste.

  The taste was sharp and bitter. As bitter as his disappointment. Itwas all a grim joke. Valuable enough once to be used as money in theold days on earth. But hardly valuable enough, then, even in realquantity, to be worth the six lives it had cost up to now--countinghis and Darbor's as already lost. First, Laird Martin, with his lasttragic thoughts of a tiny girl on Earth, now orphaned. Then the threemen down the slope, hideous in their bulged and congealing death.Himself and Darbor next on the list, with not much time to go. All fora few crystals of--Salt!

  * * * * *

  The end was as viciously ironic as the means had been brutal, butgreed is an ugly force. It takes no heed of men and their brief,futile dreams.

  Denver shrugged and rejoined his small garrison. The girl, in spite ofthe comradeship of shared danger, was as greedy as the others outside.Instinctively, Denver knew that, and he found the understanding inhimself to pity her.

  "Are they still out there?" he asked needlessly.

  Darbor nodded. "What did you find?"

&
nbsp; He debated telling her the truth. But why add the bitterness to thelittle left of her life? Let her dream. She would probably die withoutever finding out that she had thrown herself away following a mirage.Let her dream and die happy.

  "Enough," he answered roughly. "But does it matter?"

  Her eyes rewarded his deceit, but the light was too poor for him tosee them. It was easy enough to imagine stars in them, and even a manwithout illusions can still dream.

  "Maybe it will matter," she replied. "We can hope for a miracle. Itwill make all the difference for us if the miracle happens."

  Denver laughed. "Then the money will make a difference if we livethrough this? You mean you'll stay with me?"

  Darbor answered too quickly. "Of course." Then she hesitated, as ifsomething of his distaste echoed within her. She went on, her