I want to thank my wife, Elizabeth Hill, my editor, Victoria Wilson, and my agents, Gail Hochman and Lynn Pleshette, for their very generous assistance in the completion of this book. The following people also read the manuscript in a still-unfinished state and offered criticism and comments that were invariably helpful: Michael Cendejas, Stuart Cornfeld, Carlyn Coviello, Carol Edwards, Marianne Merola, John Pleshette, Doug and Linda Smith, and Ben Stiller. I thank them all.

They met Mathias on a day trip to Cozumel. They'd hired a guide to take them snorkeling over a local wreck, but the buoy marking its location had broken off in a storm, and the guide was having difficulty finding it. So they were just swimming about, looking at nothing in particular. Then Mathias rose toward them from the depths, like a merman, a scuba tank on his back. He smiled when they told him their situation, and led them to the wreck. He was German, dark from the sun, and very tall, with a blond crew cut and pale blue eyes. He had a tattoo of an eagle on his right forearm, black with red wings. He let them take turns borrowing his tank so they could drop down thirty feet and see the wreck up close. He was friendly in a quiet way, and his English was only slightly accented, and when they pulled themselves into their guide's boat to head back to shore, he climbed in, too.

They met the Greeks two nights later, back in Cancún, on the beach near their hotel. Stacy got drunk and made out with one of them. Nothing happened beyond that, but the Greeks always seemed to be turning up afterward, no matter where they went or what they were doing. None of them spoke Greek, of course, and the Greeks didn't speak English, so it was mostly smiling and nodding and the occasional sharing of food or drinks. There were three Greeks-in their early twenties, like Mathias and the rest of them-and they seemed friendly enough, even if they did appear to be following them about.

The Greeks not only didn't know English; they couldn't speak Spanish, either. They'd adopted Spanish names, though, which they seemed to find very amusing. Pablo and Juan and Don Quixote was how they introduced themselves, saying the names in their odd accents and gesturing at their chests. Don Quixote was the one Stacy made out with. All three looked enough alike, however-wide-shouldered and slightly padded, with their dark hair grown long and tied back in ponytails-that even Stacy had a hard time keeping track of who was who. It also seemed possible that they were trading the names around, that this was part of the joke, so the one who answered to Pablo on Tuesday would smilingly insist on Wednesday that he was Juan.

They were visiting Mexico for three weeks. It was August, a foolish time to travel to the Yucatán. The weather was too hot, too humid. There were sudden rainstorms nearly every afternoon, downpours that could flood a street in a matter of seconds. And with darkness, the mosquitoes arrived, vast humming clouds of them. In the beginning, Amy complained about all these things, wishing they'd gone to San Francisco, which had been her idea. But then Jeff lost his temper, telling her she was ruining it for everyone else, and she stopped talking about California -the bright, brisk days, the trolley cars, the fog rolling in at dusk. It wasn't really that bad anyway. It was cheap and uncrowded, and she decided to make the best of it.

There were four of them in all: Amy and Stacy and Jeff and Eric. Amy and Stacy were best friends. They'd cut their hair boyishly short for the trip, and they wore matching Panama hats, posing for photos arm in arm. They looked like sisters-Amy the fair one, Stacy the dark-both of them tiny, barely five feet tall, birdlike in their thinness. They were sisterly in their behavior, too, full of whispered secrets, wordless intimacies, knowing looks.

Jeff was Amy's boyfriend; Eric was Stacy's. The boys were friendly with each other, but not exactly friends. It had been Jeff's idea to travel to Mexico, a last fling before he and Amy started medical school in the fall. He'd found a good deal on the Internet: cheap, impossible to pass up. It would be three lazy weeks on the beach, lying in the sun, doing nothing. He'd convinced Amy to come with him, then Amy had convinced Stacy, and Stacy had convinced Eric.

Mathias told them that he'd come to Mexico with his younger brother, Henrich, but Henrich had gone missing. It was a confusing story, and none of them understood all the details. Whenever they asked him about it, Mathias became vague and upset. He slipped into German and waved his hands, and his eyes grew cloudy with the threat of tears. After awhile, they didn't ask anymore; it felt impolite to press. Eric believed that drugs were somehow involved, that Mathias's brother was on the run from the authorities, but whether these authorities were German, American, or Mexican, he couldn't say for certain. There'd been a fight, though; they all agreed upon this. Mathias had argued with his brother, perhaps even struck him, and then Henrich had disappeared. Mathias was worried, of course. He was waiting for him to return so that they could fly back to Germany. Sometimes he seemed confident that Henrich would eventually reappear and that all would be fine in the end, but other times he didn't. Mathias was reserved by nature, a listener rather than a talker, and prone in his present situation to sudden bouts of gloom. The four of them worked hard to cheer him up. Eric told funny stories. Stacy did her imitations. Jeff pointed out interesting sights. And Amy took countless photographs, ordering everyone to smile.

In the day, they sunned on the beach, sweating beside one another on their brightly colored towels. They swam and snorkeled; they got burned and began to peel. They rode horses, paddled around in kayaks, played miniature golf. One afternoon, Eric convinced them all to rent a sailboat, but it turned out he wasn't as adept at sailing as he'd claimed, and they had to be towed back to the dock. It was embarrassing, and expensive. At night, they ate seafood and drank too much beer.

Eric didn't know about Stacy and the Greek. He'd gone to sleep after dinner, leaving the other three to wander the beach with Mathias. There'd been a bonfire burning behind one of the neighboring hotels, a band playing in a gazebo. That was where they met the Greeks. The Greeks were drinking tequila and clapping in rhythm with the music. They offered to share the bottle. Stacy sat next to Don Quixote, and there was much talking, in their mutually exclusive languages, and much laughter, and the bottle passed back and forth, everyone wincing at the burning taste of the liquor, and then Amy turned and found Stacy embracing the Greek. It didn't last very long. Five minutes of kissing, a shy touch of her left breast, and the band was finished for the night. Don Quixote wanted her to go back to his room, but she smiled and shook her head, and it was over as easily as that.

In the morning, the Greeks laid out their towels alongside Mathias and the four of them on the beach, and in the afternoon they all went jet skiing together. You wouldn't have known about the kissing if you hadn't seen it; the Greeks were very gentlemanly, very respectful. Eric seemed to like them, too. He was trying to get them to teach him dirty words in Greek. He was frustrated, though, because it was hard to tell if the words they were teaching him were the ones he wanted to learn.