Chloe sits upright in her seat, willing the scenery to flash past faster at the windows. Even two inches closer to the edge of her seat will mean she pulls in to London quicker. When the trolley comes around she buys a KitKat and a Diet Coke. It fizzes as she pours it into a beige plastic cup.

The train heads out to the edges of Fenland. There is still frost on the ground and birds stand on the woolly backs of sheep to keep their feet warm. Everyone is useful to someone.

Takeaways and betting shops lead Chloe to Acton police station from the tube, and like a trail of breadcrumbs these garish signs will lead her back the way she came. When she reaches the counter she’s panting, as if she had been holding her breath all the way from Peterborough.

‘My nan . . . Grace Hudson . . . she’s h— I mean, she’s been found. She’s here.’

The officer behind the counter gestures for her to slow down.

‘OK, let’s start at the beginni—’

‘It was PC Bains who called me, she . . . she said Nan was here, that she was fine. Dehydrated. Please, I just need to see her.’

‘OK, OK . . .’ the officer says, more sympathetic than impatient. He taps something into his computer. ‘Can you tell me your grandmother’s name?’

‘Grace. Grace Hudson.’

Chloe scans his face for recognition while he studies his computer screen. She learnt a long time ago to read faces for the bits people don’t tell you.

‘Would you like to take a seat and I’ll let PC Bains know you’re here.’

‘Is she here? Nan, I mean.’

‘If you could just take a seat,’ he says. He indicates towards the bench behind her, blue and shiny, matching the Met Police logo.

Chloe waits in reception – just like on the train – on the very edge of her seat. She scans each person in uniform who walks by in case she can identify PC Bains. She distracts herself by picking the dry skin around her nails until red bleeds into her cuticles.

She hears a voice down the corridor. Nan’s voice. She looks up. PC Bains is walking along the corridor towards her, her arm hooked around Nan’s elbow, talking to her as if they’re old friends. Chloe stands up and rushes towards them like she knows for sure they’d do in films.

‘Nan,’ she says.

Nan looks at her like they saw each other just five minutes before.

‘Chloe, whatever’s happened, dear? You look like you’ve seen a ghost.’

PC Bains pats her arm. She has a Brummie accent when she speaks. ‘She’s been worried about you, Grace. You went wandering, didn’t you? You’ve caused your poor granddaughter all sorts of worry.’

‘I don’t have a granddaughter.’

PC Bains gives Chloe a sympathetic look.