It was only once she was out on the rubbish-strewn pavement that Lou regained the presence of mind to take a step back through the gates. Her trainer changed back to a brown boot in the snow. She hadn’t outstayed her welcome, not yet anyway.

At the library, Mrs Rogers glanced up when Lou passed her on the way to the office at the back. She knocked on the door, and Will beckoned to her through the window.

‘You came back.’ He smiled.

‘Is this a bad time?’ she asked, taking in the plastic sandwich box on the desk.

‘Couldn’t be more perfect.’ Will screwed up an empty crisp bag and dropped it in the wastepaper basket. He patted the chair beside him. ‘I hoped you’d come. Our chat yesterday got my research antennae twitching. I was up half the night looking into those Mandevilles and Caxtons of yours.’

‘Sorry.’

‘Don’t be. I’ve been itching to share this with you.’ He pulled a lever arch file from an oversized battered satchel on the floor and pushed it across the desk. Lou stared in awe at the hefty brick of paper between the black covers of the file. She knew only too well that that level of research was the result of burning the midnight oil until it ran dry.

‘You’ll have to let me pay you for the paper and ink,’ she said.

Will looked at her from beneath his fringe. ‘I wouldn’t hear of it. If I’m honest, you did me a favour. I’m staying with my cousin while I’m on my placement, and this gave me an excuse to stay in my room and steer clear of her kids. I’m not sure how much more In the Night Garden I can take.’

Lou smiled. Will really was a very sweet guy.

‘I digress.’ Will patted the file. ‘The Mandevilles and Caxtons are fascinating. They had a ridiculously tangled past. This isn’t even the half of it. I could have gone on searching all night. But, you know, I need my beauty sleep.’ He waggled his eyebrows, but Lou was fixated on the contents of the file and didn’t respond.

Will coughed. ‘Anyway, I’ve been doing my best to unpick what I can. You said you were interested in the First World War period, so I used that as my starting point. It was like reading a blockbuster, but better than the Da Vinci Code any day.’

Will’s eyes shone with what Lou recognised as the thrill of the research chase; the joy of unearthing disparate facts and documents that had lain unread for decades or centuries and joining the dots to get to the truth of the story. She had to fight the instinct to tear into Will’s carefully prepared file. He had to be allowed the satisfaction of the reveal. And he might think it odd if she seemed too keen. She wasn’t supposed to know anything about the history of the Mandevilles and Caxtons.