His first thought was Twins.

But that was ridiculous. Alex looked too much like his dad not to be his son—the ginger hair, the freckles, the shape of the eyes and nose—and he’d inherited his mum’s asthma. Flip’s features—his hands, the shape of his face—were all wrong; he was too dark, too tall, too different to be a Gray. No, Alex and Philip weren’t twins, but there remained the coincidence—too amazing to be a coincidence—that fourteen years and eight months ago, they’d come into existence on the very same day.

It felt like a revelation. What it revealed, though, Alex had no idea.

Back at the Garamonds’, there was his first dinner to survive. Spaghetti Bolognese. Flip’s parents were drinking wine. So was Teri. No way would Mum and Dad let him drink alcohol at the tea table even if he was seventeen. They wouldn’t have drunk themselves when there was work the next day. And they’d not all be eating together like this, as a family. At home, except on special occasions, Alex and Sam ate off their laps while they watched TV. Mum and Dad had their dinner later. As for the food, Mum wasn’t a bad cook; it was just … actually, she was bad. Dad was worse. But Alex was used to their cooking; they knew what he’d eat and what he wouldn’t. After the croissants fiasco, he’d been dreading this meal. But Alex loved spag bol. And this was the best he’d ever tasted. The garlic bread, too. Fantastic. Homemade. Even the salad was edible, if you pushed the tomatoes and bits of beetroot to the side of your plate. And the spring onion. And the radish.

“This is absolutely delicious, Mrs. Garamond,” Alex said.

The dad looked up from his plate, mouth open in mid-chew. The sister let out a snort. Flip’s mother rescued Alex, unwittingly, by playing along with the “joke.” “Why thank you, young man—you may dine with us again.”

She laughed and the others did, too, if a little uncertainly. Alex flushed and concentrated on his food, head down. Mrs. Garamond. What had he been thinking?

Again, the mother bailed him out, with a change of subject. “There won’t be time in the morning,” she said, addressing Teri, “so I’ve put a packed lunch in the fridge for you. Remind me to remind you to take it out when you leave for school.”

Flip’s dad ripped off a piece of garlic bread. “What’s this, then, Ter?” he said, dunking the bread in his Bolognese. “You off somewhere?”

“Malham,” she said. “Geology field trip.”

“Limestone pavement,” the dad said, eating and talking. “Clints and grikes.”

“Thanks for that, Dad.” Teri acknowledged him with a wave of her fork. “I don’t need to go on the trip now—you’ve taught me all there is to know.”

“I’ll bet you didn’t know that limestone—”

“Chin, Michael,” Flip’s mum said, pointing. “Sauce.”

They were posh, the parents. Posher than the daughter. Less Yorkshire—not Yorkshire at all, really. Alex stole a glance at Flip’s dad. About fifty. Going thin on top. Glasses. His stubble was dark, bluey black, and when he wiped his chin, you could hear the rasp of the napkin (a proper cloth one). Alex wondered what he did for a job. The mum, too. He pictured her owning a boutique. As for the dad, something office-y, given the flabby jowls and belly; he was like a gone-to-seed version of Flip.

“How did you get on at nets?” the dad said suddenly. He didn’t look up from his food as he spoke, so it took Alex a moment to realize that the question was for him. Nets? What are nets? Before he could think of how to answer, Flip’s father, perhaps seeing his confusion, added, “Isn’t it cricket practice after school on a Tuesday?”

“It is, dear,” Mrs. Garamond said, “but today’s Monday.”

“Is it?”

“He had something after school,” Teri said. “He was later home than me. ”

Alex looked at her across the table. Did she know about Ms. Sprake’s keeping him back? Teri was in the sixth form, he figured, but maybe she’d heard about his run-in with Johannsen and was set to drop him in it. She didn’t. She was working another angle. Smirking, she said, “Donna, yeah? Biology homework?”

“Donna?” the dad said. “Who’s Donna?”

“This month’s eye candy. He’s gone for an intelligent one this time: she has two brains … one in each tit.”

“Teri, language.”

“Is Donna the redhead?”

“No, Dad, that was Abby. She is so last month.”

“I quite liked her.”

“Dad, in her Bebo profile she says her ambition is to be a ‘glammer model.’ That’s ‘glamour,’ double m, e-r.”

“Well, she was certainly—”

“Are we going to get to meet this Donna?” the mum said, smiling warmly at Alex. She was already one glass of wine ahead of the dad.

“I don’t know,” Alex said. “I haven’t met her myself yet.”

None of them seemed to know what he meant by this, or whether it was a joke. In the awkwardness that followed, the mum and dad drifted to other topics and it was only Teri who continued to watch Alex, like someone who’s added a column of figures twice and come up with different totals. She’d have been about three when Flip was born, and had probably been excited at the arrival of a baby brother. Hard to imagine that now. Or Mrs. Garamond in a hospital bed somewhere, giving birth to Philip on the same day that Alex’s own mum was having him.

Two brains, one in each tit. Alex liked that. She was quite funny, Flip’s sister. If she didn’t detest him, they might get along okay.

For the rest of the meal, Alex said as little as possible. Pudding, which they called dessert, was fresh-fruit salad. Very nice it was, too. You’d get your five a day here, no problem. At home, he’d factored in tomato ketchup and was still four short.

Afterwards, Alex raised eyebrows again by helping, unprompted, to clear the table. Teri made a display of standing there dumbfounded. Flip’s mum warned him that if this was a ploy to delay his homework … But he pressed on, fetching plates, bowls, glasses, cutlery, scraping and rinsing, passing things to the dad for loading into the dishwasher. The women left them to it. The men talked—at least, Mr. Garamond did—a monologue about one of his undergraduates (so, he was a lecturer) whose essay on “the relationship between tyranny and republicanism in ancient Rome” was almost entirely cut-and-pasted from Wikipedia. Alex half listened, half watched. What was it with dads and dishwashers? His own father was the same: acting like the future of humankind depended on the exact arrangement of each item in the racks.

“Can I ask you something?” Alex said. He’d managed not to address him as Mr. Garamond but couldn’t bring himself to call him Dad, so he didn’t call him anything at all. “Do you believe in the soul?”

“The soul?” Flip’s dad paused in mid-stack, looked at Alex. “Is this something you’re doing at school?”

“For religious studies, yeah. Like, a project.”

He knew what his own father would’ve said: The soul! They’ll be teaching you about tooth fairies next. GCSEs in Father Christmas studies. But Flip’s dad seemed to be giving the question serious consideration. The university lecturer, being asked to apply his intelligence to a complex subject.

“Hmm, the soul,” he said, frowning, the plate in his hand dripping gunk onto the floor. “Well, it depends whether you look at it as a concept or as an actual, physical—” Which was as far as he got before being distracted by his wife’s reappearance in the kitchen. She went to the back door, opened it and peered into the garden.

“Have either of you seen Beagle?”

“Shit,” Alex said. “I’ve left him tied up outside the library.”

From their expressions, it wasn’t clear what had startled Flip’s parents: that he’d sworn, that he’d forgotten the dog, or that he’d been to the library.

Alex was banished to the bedroom to do his homework. Once he’d retrieved Beagle, of course, who had fallen asleep where he’d been left and who—not unreasonably, in the circumstances—gave Alex another nip when he unfastened the lead from its post.

The homework (recasting sentences in the past, present and future tenses for French) was straightforward enough. Half an hour and it was done. Which left the rest of the evening to have a proper snoop in Flip’s room. He had to find out more about the boy he’d been paired with. Or uncover some clue, maybe—something odd in Flip’s life in the period leading up to the “switch,” as he’d come to think of it. As far as he could recall, there was nothing unusual from his own life back then.

“Back then” being the day before to Alex, or the past December to Philip.

He switched on the PC once more. E-mail and the Internet might be off-limits without a password, but he could at least trawl around My Documents, My Music, My Pictures and the memory stick from the schoolbag. Bits of schoolwork; a file containing a list of the Greatest Cricketers of All Time, divided into categories (bowlers, batsmen, wicket-keepers, allrounders); homework notes; a copy of a letter, dated more than a year earlier, from Flip to someone called Kevin Pietersen, asking which was the best guard to take: leg, middle-and-leg or middle. Alex had no idea what this meant. Flip’s My Pictures folder was empty, apart from the stock of desktop wallpapers. As for the music on his PC—and his iPod and the CDs in the rack on his desk—it was almost exclusively rap. Alex would’ve sooner punctured his eardrums with a kebab skewer than listen to any of it.

The diary section of Flip’s planner revealed nothing unusual in the days before June 23, or six months earlier, when Alex had spent the evening at David’s, then legged it home. Searching the room, he only found more evidence of the differences between him and Flip rather than similarities, let alone connections. The books (very few) were mostly nonfiction: sport, true crime, the Viz annual, Windows for Dummies, ex-SAS memoirs. In the bottom of the wardrobe were a new-looking pair of in-line skates, a cricket bat, golf clubs, a tennis racket, various balls, dumbbells and—please, no—a skateboard. The clothes were okay. Cool. Expensive. The right brands from the right shops. Alex stripped off the school uniform and tried on a few combinations. They fitted. Well, of course they did. They looked great, too, in the full-length mirror on the back of the wardrobe door. So did he, for once.

Alex ransacked various drawers but turned up nothing of any use. He felt a brief flare of optimism when he came across a card for a Halifax account, but almost as soon as he imagined raiding Flip’s savings to get home, Alex realized he’d need the PIN.

It did at least make him aware of what he wanted to do more than anything. More than solving the mystery of what had paired him with Flip in the first place. If Alex was unable to contact his mother, David or anyone from his “real” existence, then he must go to them. Go home. Make them see him for who he was. Beagle did. If a dog could tell this version of Flip from the genuine one, surely Alex’s parents, his brother, his best mate could sense that he was in there, behind this impostor’s facade.

Somehow, Alex had to see Mum and Dad, face to face.

This time he was underwater, running, feet sinking deeper and deeper into the seabed. The surface was within reach if he raised his arms, but he couldn’t get his head out of the water. He had to breathe. The compulsion to inhale was huge. But he couldn’t, mustn’t. Still he ran, getting nowhere, each frantic step burying his feet in the wet sand until he was no longer able to lift them. Finally, with one great gulp, he opened his mouth, his lungs to the flood of foul seawater.

Alex woke. Sat up in bed. His heart was racing and he gasped for air as though he’d actually been drowning.

Was this his asthma, back again? Twenty-four hours after the switch, had he returned to his own body? He fumbled for the bedside light, almost knocking it to the floor. The sudden brightness blinded him. But when he was able to open his eyes, one look at that forearm, the hand, the fingers, told him all he needed to know.