magine you’re a polar bear and you find yourself in the middle of a rainforest. There are flying squirrels, and monkeys, and bright green frogs, and you have no idea how you got there or what you’re supposed to do next. You’re lonely, you’re lost, you’re frightened and all you know – for absolute certain – is that you shouldn’t be there.

Now imagine you find another polar bear. You’re so happy to see another polar bear – any polar bear – that it doesn’t matter what kind it is. You follow that polar bear around, just because it’s not a monkey. Or a flying squirrel. Because it’s the only thing that makes it OK to be a polar bear in the middle of a rainforest.

Well, that’s how it is with Toby. One geek, incoherently happy to find another geek in the middle of a world full of normal people. Thrilled to discover that there is someone else like him. It’s not me he wants. It’s my social standing. Or lack thereof.

And let me get something straight: I’m not going to have a romance with someone just because they’re made out of the same stuff as me. No. I’d rather be on my own. Or – you know – in unrequited love with a parrot. Or one of those little lemurs with the stripy tails.

“Harriet!” Toby says again and a little bit of bogey starts dripping from his nose. He promptly wipes it on his jumper sleeve and beams at me. “I can’t believe you came!”

I glare at Nat and she grins, winks and goes back to reading her magazine. I am not feeling very harmonised with her at the moment, if I’m being totally honest. In fact, I sort of feel like hitting her over the head with my crossword puzzle.

“Yes,” I say, trying to edge away. “Apparently I had to.”

“But isn’t this just wonderful?” he gasps, clambering up on to his knees in his unbridled enthusiasm. I notice that his T-shirt says THERE’S NO PLACE LIKE 127.0.0.1. “Of all the buses in all the towns in all the world, you walk on to mine. Can you see what I did there? It’s a quote from Casablanca, except that I replaced the words gin joints with bus and the word into with on to.”

“You did, yes.”

Nat makes a snuffle of amusement and I subtly pinch her leg.

“Do you know what I learnt this morning, Harriet? I learnt that the phrase rule of thumb came from a time when a man was only legally allowed to beat his wife with something the width of his own thumb. I can lend you the book, although there’s a pizza stain on page 143 which you might have to read round.”

“Erm. Right. Thanks.” I nod knowingly and then lift my book so that Toby realises the conversation is over.

He doesn’t.

“And,” he continues, holding it down so he can see me properly. “You know the most unbelievable thing?”

It’s funny, when Toby behaves like this, I can suddenly see why I’m so annoying.

“Well, did you know that…” The coach swerves slightly into the middle lane. Toby swallows. “That…” he continues and licks his lips. The coach swerves back into the slow lane. “That—” Toby’s face goes abruptly green and he clears his throat. “I don’t want you to think I’m easily distracted, Harriet,” he finally continues in a little voice, “but I’m suddenly not feeling so well. I don’t take too kindly to vehicles, particularly the ones that move. Do you remember the ride-on lawnmower in Year One?”

I look at him in horror and Nat immediately stops smirking. “Oh, no,” she says in a dark voice. “No, no.” Nat obviously remembers it too.

“Harriet,” Toby continues, licking his lips again and going an even stranger colour. “I think we might need to stop the bus.”

“Toby,” Nat snaps in a low, warning voice. “Breathe in through your nose and out through your—”

But it’s too late. The coach makes one more sudden movement and – as if in slow motion – Toby gives me one look of pure apology.

And vomits all over my lap.