So Sally and Rob wouldn’t have fallen in love, gotten married after college, had a child. And when the time came to make their wills, they wouldn’t have chosen Julia to be the guardian of their child should anything happen to them.

And one night when the child was nine, if the cab they’d ordered hadn’t failed to pick up Sally and Rob from the restaurant outside Hopton, Connecticut, where they’d been celebrating their tenth wedding anniversary, they wouldn’t have decided to walk home along the road instead.

And if the girlfriend of someone named Sean Hodges hadn’t dumped him for being a loser, he wouldn’t have gotten drunk and cried and driven over to her place. And if she’d taken him back or let him in, he wouldn’t have driven home again, angry and still drunk, and he wouldn’t have hit two people walking along a dark and quiet country road, killing them.

So as much as they’d never really imagined it happening, Sally and Rob’s child, nine-year-old Tom Calloway, ended up in the guardianship of their oldest friend. But, it has to be said, she was someone they hadn’t really had much to do with in recent years. In truth, they’d tired of her woes and her flakiness, but even if it had ever crossed their minds to amend their wills, death had caught up with them first.

And being landed with the responsibility of looking after a child had little impact on Julia’s lifestyle. So it didn’t matter eight years later that a school trip to Costa Rica for a special environmental project was completely not the sort of thing Tom would usually do, because Julia wanted to go on a yoga retreat in Italy, and the dates fit perfectly. So in the end, to escape her pleading, Tom agreed to go to Costa Rica, a place he didn’t want to visit, with people he didn’t want to be with, to do things he didn’t want to do.

And that’s the butterfly effect. If a jerk named Matt Nicholson had not spiked the drinks of a girl named Sally Morgan, Tom Calloway, if he’d been born at all, would not have been boarding a plane more than twenty years later, a plane that, unbeknown to Tom or any of the other people in his school party, would never reach its destination.

CHAPTER 1

It wasn’t that Tom didn’t care about the environment. He recycled and he liked those David Attenborough documentaries on TV, but he couldn’t help thinking there was a lot of hypocrisy out there too. Hypocrisy like burning a ton of fuel to fly a whole bunch of schoolkids from the richest country in the world to look at plants and butterflies in Costa Rica. He just didn’t buy it.