The more she thought about it, the better it sounded. A fun-filled weekend outing is just what the doctor ordered, she decided. For all of us.

She couldn't wait to get going.

Believe it or not," the park ranger explained, "this entire region was once at the bottom of a huge inland sea. Two hundred and fifty million years ago, these caves began as a series of underwater reefs. Eventually, however, the sea dried up and the reef was buried beneath tons of sediment. Over the centuries, geological pressures gradually pushed the reef system back toward the surface where rainwater, seeping through cracks in the limestone, began carving out the caverns all around us."Liz tried to imagine the arid Chihuahuan Desert, now about seven hundred feet above them, covered in seawater, but it was hard to visualize, especially after driving all the way down from Roswell through almost a hundred miles of sun- baked, reddish-brown New Mexican landscape. Fortunately, they had gotten off to an early start this morning, before the June heat hit its peak.

"Isn't this amazing, Max?" she said, taking in the spectacular subterranean scenery all around them. Jagged stalactites hung like gigantic stone icicles high above their heads, while fanglike stalagmites reached toward the ceiling. Massive calcite columns, formed when the stalactites met their inverted counterparts, rose dramatically like the pillars of some ancient pagan temple. In places, the limestone walls of the spacious cavern resembled frozen waterfalls, or overlapping sheets of petrified drapery. Colored lights, positioned strategically throughout the caves, displayed its natural wonders to their best advantage, providing an eye-catching array of shadows, hues, and textures. Time had polished many of the formations, giving them a pearly, opalescent sheen. It's like an alien world, Liz thought, right here on Earth.

"It is impressive," Max agreed, his arm around her waist as they strolled along with a large herd of tourists, making an effort to stay within earshot of the friendly ranger giving the group a guided tour of the King's Palace section of the caverns. Max ducked his head to whisper into her ear, "This place makes the Pod Chamber"-where he and the other alien children had been buried after the Crash- "look like a gopher hole."And this is just a small fraction of what's down here," Liz commented, flipping through the guidebook she had bought on the surface. "It says here that there are over eighty-five caverns in the Park, of which only ten or so are open to the public."You hear that, folks?" Maria chimed in. She and Michael were right behind them, followed closely by Alex and Isabel. "Nobody get lost, 'cause I don't want to go poking around in spooky, bat-filled caves looking for you."Maria was traumatized by The Adventures oj Tom Sawyer at an early age," Liz teased, recalling the sequence where Becky Thatcher and Tom were stalked through an underground labyrinth by the murderous Injun Joe. "She used to hide behind the couch whenever we got to that part on the video."Funny, I don't remember being alone behind that couch," Maria stated. She gave Liz a playful punch from behind. "Admit it, Parker, you were just as creeped-out as I was."Well, we were only ten at the time," Liz said. "1 like to think I'd be a bit braver now."After the Skins and the Special Unit," Max said, "I'm sure of it." He tightened his hold on her waist, giving her an affectionate squeeze.

"Just the same, everybody stick to the lighted trails," Maria insisted, clearly getting in touch with her inner Den Mother. "And, remember, if we get separated, everybody meet back at the elevator."Michael snorted. "Like I'm really going to be tempted to go exploring on my own." He regarded the surrounding stalagmites and such with a distinctly unimpressed air. "I mean, it's just a humongous hole in the ground. What's the big deal?"Maria pulled away from Michael, glaring at him bale-fully. "You know, you could at least try to have a good time, for my sake. Or would that spoil your whole image as a Rebel Without a Planet?"Hey, so I don't feel like oohing and aahing over a bunch of pretty lights and rock formations. Is that such a crime?" he groused. Slouched shoulders advertised his lack of enthusiasm for the entire expedition. "Give me a break. Lighten up."By now, Maria was fuming visibly. She turned on him angrily, green eyes flashing. "No, you lighten up, Michael Guerin, and another thing…!"Sssh!" a middle-aged tourist, wearing a souvenir Carlsbad Caverns baseball cap, shushed the teenagers, an annoyed look on her face. Liz blushed, embarrassed even though it wasn't really her fault, and even Maria and Michael looked a little abashed. They all lowered their voices as they hurried to catch up with their tour guide, who was now explaining why one particular formation was known as the Frustrated Lovers. Well, that's appropriate, Liz thought wryly, particularly where Maria and Michael were concerned.

Flashbulbs flared as a mob of tourists elbowed and jostled their way forward, trying to get a better view of the petrified Lovers. The one problem with hitting the caverns on a sunny summer weekend, Liz realized, was coping with the inevitable crowds. There seemed to be hundreds of people exploring the various caverns today, which made sightseeing a bit of a hassle. The crush of would-be spelunkers squeezed the small band of high school students together, making it easier to converse without raising their voices.

"You know," Alex remarked, now that he and Isabel were right next to Liz, "this whole thing is cool and all, but I can't help thinking that the public parts of the caverns have been domesticated too much. You've got paved trails, electricity, lights, guardrails, even waste baskets every fifty yards or so." To prove his point, he slam-dunked a wadded-up candy bar wrapper into the nearest convenient trash receptacle. "Don't you think it would be spookier and more atmospheric if these caves actually looked more like caves and less like an underground mall?"I see your point, Alex," Max said amiably, sounding more at ease than he had for weeks, maybe months. "Although I think there are some more caverns nearby that have been left in something closer to their natural state, for more serious cavers, and other caves that have barely been explored at all." He leafed through the guidebook in Liz's hands. "Yeah, it says here there's Slaughter Canyon Cave, Spider Cave, and some that don't even have names yet."Now there's an idea!" Alex enthused. "What do you think, Isabel?" He grinned goofily at Max's sister. The wiry would-be musician and the pristine prom queen made an odd-looking couple, but Liz had more or less given up trying to figure out their relationship. "Later on, you want to go looking for a cave of our own?" He wiggled his eyebrows, Groucho-style, trying to coax a laugh or smile from his glamorous (but emotionally elusive) dream girl. "Just you, me, and a couple thousand bats."I don't think that would be safe," Isabel responded, more or less missing the point. Although she dutifully held onto Alex's hand, her manner remained distant and preoccupied. "Why don't we just listen to the ranger^ lecture, okay?"Yeah, sure, that's fine, I guess," Alex muttered, disappointed once again in his never-ending struggle to get past Isabel's considerable defenses. Liz had to admire his persistence, even if she sometimes thought he was fighting a losing battle.

She sighed sympathetically, taking stock of the fracture lines dividing her friends. At the moment, it seemed as though only she and Max were making the most of today's excursion. That's too bad, she thought, squeezing Max's waist even tighter, but I'm not going to let Michael and Maria's problems, or Alex and Isabel's, spoil my own day with Max. After risking her own life and happiness to save the entire world from alien invaders, she figured she was entitled to be a little bit selfish, if only for just one weekend.