“A little later. Tell Mom.”

“She’ll get it?” Marty was passing through a stage of doubting his mother’s technical skills. This irritated Arthur.

“She’s used it more than I have, buddy.”

“All right!” Marty enthused, releasing the dog, dropping the puppet and running for the steps ahead of Arthur. Gauge immediately grabbed the monkey by the throat and shook it, growling. Arthur followed his son, turned left in the hallway past the freezer chest, and picked up his office extension.

“Christopher, what a surprise,” he said affably.

“Art, I hope I’m the first. “Riley’s voice was a higher tenor than usual.

“Try me.”

“Have you heard about Europa?”

“Europe?”

“Europa. Jupiter’s sixth moon.”

“What about it?”

“It’s gone.”

“I beg your pardon?”

“There’s been a search on at Mount Wilson and Mauna Kea. The Galileo’s still going strong out there, but it hasn’t been aimed at Europa for weeks. JPL turned the cameras to where Europa should be, but there’s nothing big enough to photograph. If it were there, it would come out of occultation again in about ten minutes. But nobody expects to see it. Calls from amateurs have been flooding JPL and Mount Palomar for sixteen hours.”

Arthur couldn’t shift gears fast enough to think how to react. “I’m sorry…?”

“It’s not painted black, it’s not hiding, it’s just gone. Nobody saw it go, either.”

Riley was a rotund, crew-cut, plaid sports-coated kind of scientist, shy in person but not on the phone, deeply conservative. He had always been critically deficient in the humor department. He had never pulled Arthur’s leg on anything.

“What do they think happened?”

“Nobody knows,” Riley said. “Nobody’s even venturing a guess. There’s going to be a press conference here in Pasadena tomorrow.”

Arthur pinched his cheek speculatively. “Did it explode? Something hit it?”

“Can’t say, can we?” He could almost hear Chris’s smile in his voice. Riley did not smile unless he was faced with a truly bizarre problem. “No data. I’ve got about seventy other people to call now. Keep in touch, Arthur.”

“Thanks, Chris.” He hung up, still pinching his cheek. The smoothness of the moment by the river had passed. He stood by the phone for a moment, frowning, then walked into the master bedroom.

Francine reached high to rummage through the top shelf of the bedroom closet, Marty and Becky at her heels.

In their seventeen years together, his wife had moved over the line from voluptuous to zoftig to plump. The physical contrast between Arthur and Francine, all curves and fulfilling grace, was obvious; equally obvious was the fact that what others saw in them, they did not see in each other. She tended to wear folk art print dresses, and much of her wardrobe was a stylish acquiescence to matronliness.

Yet in his thoughts, she was eternally as he had first seen her, walking up sunny white-sanded Newport Beach in southern California, wearing a brief one-piece black swimsuit, her long black hair loose in the breeze. She had been the sexiest woman he had ever known, and she still was.

She pulled down the bulbous canvas Astroscan bag. Bending over, she rummaged for the box of eyepieces under a pile of shoes. “What did Chris want?” she asked.

“Europa’s disappeared,” Arthur said.

“Europe?” Francine smiled over her shoulder and straightened, passing the bag to him.

“Europa. Sixth moon of Jupiter.”

“Oh. How?”

Arthur made a face and shrugged. He took the telescope and its painted gray metal base and carried them outside, Gauge snorting at his heels.

“Uh-oh, kids. Dad’s in robot mode,” Francine called from the bedroom. “What did Chris really say?” She followed him down the stairs and onto the lawn, where he pressed the telescope base into the soft grass and soil.

“That’s what he really said,” Arthur replied, dropping the big red ball of the reflector gently into the three hollowed branches of the base.

Gray, dignified Grant and lithe blond Danielle stood by the railing on the east side of the rear deck, overlooking the yard and the plum tree. “It’s a lovely night,” Danielle said, holding Grant’s arm. Arthur thought they most resembled models in upscale real estate ads. Still, they were good people. “Stargazing?”

“It’s not secret or anything, is it?” Francine asked.

“I truly doubt such a thing can be kept secret,” Arthur replied, peering into the eyepiece.

“One of Jupiter’s moons has disappeared,” Francine called up to them.

“Oh,” her sister said. “Is that possible?”

“We have a friend. An acquaintance, really. He and Arthur keep each other up-to-date on certain things.”

“So he’s looking for it now?” her sister asked.

“Can you see Jupiter from here? I mean, tonight?” Grant asked.

“I think so,” Francine replied. “Europa is one of the Galilean moons. One of the four Galileo saw. The kids were going to—”

Arthur had Jupiter in view, a bright spot in the middle of the blue-gray field. Stars formed a resolving fog in the background. Two pointlike moons, one bright and one quite dim, were clearly visible on one side of the brighter planet. The dim one was either Io or Callisto, the bright probably Ganymede. The third was either in transit across the planet or in Jupiter’s cone of shadow, eclipsed — or behind the planet, occulted. He tried to remember Laplace’s law regarding the first three Galilean moons: The longitude of the first satellite, minus three times that of the second, plus twice that of the third, is always equal to half of the circumference…He had memorized that in high school, but it did him a fat lot of good now. He murmured the consequences of the law to himself: “The first three Galileans — that includes Europa — can never be all eclipsed at once, nor can they all be in front of the disk at once. If Io and Europa are eclipsed or occulted simultaneously, or in transit simultaneously…Ah, hell.” He couldn’t remember the details. He would just have to sit and wait for the four to be visible all at once, or for only three to make an appearance.

“Can we see?” Marty asked.

“Sure. I’m going to be out here all night, probably,” Arthur said.

“Not Becky,” Danielle said.

“Oh, Mooommm! Can’t I see?”

“Go ahead,” Arthur encouraged, leaning back. Marty squatted next to the telescope and showed his cousin how to look into the eyepiece. “Don’t knock it,” Arthur warned. “Francine, can you get me the field glasses?”

“Where are they?”

“In the hall cupboard, above the camping gear, in a black leather case.”

“What would cause a moon to disappear? How big a moon is it?” Grant asked.

“It’s quite large as moons go,” Arthur said. “Rock and ice, probably with a liquid water layer under an ice shell.”

“That’s not like our moon, is it?” Danielle asked.

“Very different,” Arthur said. Francine handed him the glasses and he trained them on the sky in the general vicinity of Jupiter. After a few moments of sweeping and focusing, he found the dot of light, but couldn’t hold the glasses still enough to make out moons. Becky pulled away from the telescope, rubbing her eye and making a face. “That’s hard,” she said.

“All right. Let me use it again,” Arthur said.

Marty asked his cousin if she had seen it.

“I don’t know. It was hard to see anything.”

Arthur applied his eye to the eyepiece and found a third moon visible, also comparatively dim. Callisto, Io, and bright Ganymede. No sign of a fourth.

The rest of the family soon tired of the vigil and went inside, where they played a noisy game of Scrabble.

After two hours of straining his eyes, Arthur stood up. He felt dizzy. His legs tingled painfully from the knees down. Francine returned to the backyard around ten o’clock and stood next to him, arms folded.

“You have to see for yourself?” she asked.