“Thank you, thank you, but chocolate gives me terrible migraine. Terrible. The police? Oh, just the usual procedural stuff. What where when, had your dad been suffering from unusual stress, had we noticed any…uncharacteristic behaviour recently.”

“Had you?”

Paul McCabe spread his hands apologetically.

“Everett, you know me. I'm the last person finds out what's going on in my own department. Though, if you don't mind, perhaps I could turn your question back on you?”

“What do you mean?”

“Had you noticed your dad behaving…uncharacteristically, recently?”

Everett pictured Tejendra in his mind, flicking through moments, memories, Saturday afternoons, Sunday mornings like snapshots. The moments on the Skype calls when Everett found himself talking to dead air, Tejendra distracted, somewhere else. The time on the stand at White Hart Lane when he completely missed a sweet Danny Rose goal because he'd been frowning at a message on his iPhone. The time he'd pedalled straight past Everett outside the Tate Modern when they went to the opening night of the Rothko exhibition. Moments, memories, little snapshots when Tejendra seemed in another world entirely. A common thread held all those moments of strange together.

“You know the double-slit thing?”

“What? The experiment?”

“The classic experiment. That's what Dad said. The classic experiment that shows that reality is quantum. It starts just asking what light is made of, is it a particle or is it wave, and it's so simple, just light and shadows. But when you get really close in, really up tight and detailed, it's not one or the other. It's both and. Both and neither. He really wanted me to get it, to see how it worked. He'd explain it to me again and again. It's not the particle going through two slits at the same time; it goes through one slit in this universe, and through the other in another universe.”

“When was this, Everett?” Paul McCabe held his mug in two hands, watching Everett over the top of it like a clever bird. He took a sip of tea.

“Back just after school started again. I mean, we always talked about physics and stuff, but just all of a sudden he really needed me to understand it. Maybe it was going into year ten. And you know something? I did understand it. I saw how it worked, I knew what it meant. I understood the Many Worlds Theory.”

“Now you know what Richard Feynman said, Everett.”

“'I think I can safely say that no one understands quantum mechanics.'” Everett held Paul McCabe's gaze. The scientist looked away. Nothing was ever direct with Paul McCabe. Everett had been to the department enough times to see how he worked with his staff: a suggestion here, a hint there, a glance. “But what if I do?”