Sophie had surprised Georgia by coming to collect her when she got home for Christmas holidays. Georgia remembered whipping her coat off her hook in the year-four cloakroom and belting out to hug a student edition of her sister, with dyed hair, new glasses and a whiff of cumin and joss sticks.

As she walked on, Georgia saw people entering church for evening service. She could see herself on a pew watching candles flicker but still felt tearful from seeing her old school and worried that the greeters handing out hymn books in their bright yellow sweatshirts would ask her business.

Georgia’s heels were painful by the time she got to the town centre. She wished she’d put on her comfy Nike Frees as she queued for a latte and a pain au chocolat in Costa Coffee at the mainline station.

She people-watched as the mug warmed her hands. Couples meeting for date night, two fat men in fluorescent Network Rail vests arguing in Polish. Most touching was a lonely old guy, who counted out coins for the cheapest filter coffee and tried to make conversation with disinterested staff. Trembling hands sent his coffee dribbling and a woman with twins in a buggy shot up to help him find a seat.

When Georgia heard a message ping, she slid out her phone, imagining a stiffly phrased text from her dad, calling her irresponsible and offering to pick her up in the car. But Georgia’s screen had no message icon. The woman at the table behind had set the same sound.

Georgia watched her reflection in Costa’s plate glass. The woman flicked back bleached hair and smiled as she tapped her phone at hyper-speed. Bing – a reply. Bing – another message. Bing, bing … Then her friend arrived. Georgia noticed they had the same build and both wore striped tights as they hugged and cooed.

‘It’s been ages, sis … My God, I love your hair!’

I used to have a sister …

When they were gone, Georgia stared at the dead milk foam around the inside of her cup, and thought about how hardly anyone ever messaged her. She wasn’t disliked, and knew plenty of boys were after her, but Georgia had always found schoolwork and hobbies more interesting than the gossip and overblown dramas around which her fellow teens built friendships. Or, as they put it, Georgia was a geek.

Georgia felt a chill of dread. She’d doubted her life choices a thousand times since reading Sophie’s letter. It was like being locked in a room, forced to listen to the same song, over and over. And your brain doesn’t have an off switch.

You’re just like me. Don’t end up the same … Be happy.

But how can I be happy, Sophie Pack? Georgia asked furiously. If you knew, you’d still be here …

‘Georgia?’ someone asked, startling her out of thought.