Mirren bit her lip, rather awkwardly.

‘I was just going to say ... just to you. There’s one more ...’

He pressed a piece of paper into her hand.

‘This isn’t the writer’s place ... it’s the artist’s. His country retreat. Worth asking. And maybe ... I mean, it’s up to you, but maybe go alone.’

Mirren pondered this as Theo cheerfully accompanied her to the Writers’ Museum, which was down the Royal Mile, a chilly but beautiful walk down the long cobbled street from Edinburgh Castle to Holyrood Palace, past little hidden closes, ancient tenement buildings in higgledy-piggledy order; streets peeling off to the side, down to the Cowgate, or back to the gardens. They stopped, of course, at every bookshop they saw. It was fascinating, following the footsteps of a thousand-year-old city. To their left was a tour to Mary King’s Close, an old plague street that had been closed up four hundred years ago, leaving the inhabitants to their miserable fates, then built over. Mirren shuddered. ‘That’s not very Christmassy,’ she said.

‘You’re right,’ said Theo. ‘They should put fairy lights on all the unmarked graves.’

Mirren tutted, but was thoughtful about what Ramsay had said. Mind you, she had known him for five minutes, whereas she and Theo had spent a lot of time together. Of course, she had flattered herself that that was because he enjoyed her company, although last night had rather put paid to that ... It was a conundrum. Regardless, she didn’t mention the paper Ramsay had given her right away.

The museum, on Lady Stair’s Close, was beautiful, an old building full of treasure from three of Scotland’s most famous writers, and included memorabilia from Stevenson’s travels,pictures and objects. It was fascinating, and the woman there was incredibly informative and helpful. But nothing about the book; she knew a lot about his travels and his life, rather less about details of specific editions. It was a bust.

The Stevenson house wasn’t much help either; although the couple who now ran it as a B&B were completely delightful, they had never even heard of the book.

As Mirren and Theo came up from Heriot Row, there was definitely a flatness around them, even as the early dark had flared the city into brightness; everywhere, people were going to restaurants and bars and celebrating the run-up to Christmas in defiance of the cold dark starry night.

They had travelled a very long way, looked at miles of shelving, met a lot of people – but got no closer to their goal. As they stood there, Mirren still utterly freezing, her phone beeped. The RAC had made it to her vehicle and reckoned they’d fixed it. (She had left it open, upon reassuring herself that it was very unlikely that anyone would want to steal the spare swimming kit she kept in the boot in case she ever wanted to do some emergency exercise. It had never been used.)

‘Well,’ said Theo, crestfallen. He had felt sure that in this great city of books, surely, surely they would find the one they were looking for. ‘I’ve heard there’s an amazing shop over in Wigtown ...’

Mirren looked around. Getting the car fixed had absolutely cost the last of her money. She wasn’t going to ask her poor aunt for more; Nora sounded more and more pessimistic whenever Mirren texted. She couldn’t leave her car for much longer, it would get towed. And there would, after last night, obviously be no more sharing-a-room-with-Theo shenanigans. That had not worked out at all.

They had tried. It had been, in its way, an adventure. But here, on an ancient street in an ancient capital, revellers all around in party hats with streamers and crackers, lights swinging across the roads from the tops of buildings, Christmas tree lights glowing in the windows, it felt like it was coming to its end. It had been undeniably fun and interesting. Mirren realised as she looked around that, somehow, even the thought of Rob had ceased to sting. But her aunt was far away, getting weaker every day. If anyone would have known, she sensed, it was the old man with the missing finger in a huge cave full of books in the home town of Stevenson himself. And he did not. Edinburgh, beautiful as it was, was for her the end of the line.

Chapter 24

‘Are you seriously going to drive all the way back to London tonight?’ said Theo, as they trudged back down the ancient stone steps that led to the railway station.

‘It’ll be fine,’ said Mirren.

‘I’d be happy to share the driving ...’

‘You’ve done more than enough,’ said Mirren. ‘Thank you so much.’

A direct train to London came first and, rather reluctantly, Theo got on it, encouraged by Mirren. It was not the kind where you could pull the window down. Instead, he kept pressing the button to open the door, which was not nearly so romantic and tended to beep loudly in their ears. Nonetheless, as the departure time approached, he still leaned out of it.

‘In the absence of being able to exchange letters,’ said Theo, ‘could I ... could I perhaps take your number?’

Mirren couldn’t help smiling as they swapped. ‘Can you Snapchat me?’ he said. ‘Then I can at least see from the map that you’re on your way home, and not upside down in a ditch.’

‘You are unflatteringly worried about my driving,’ said Mirren.

‘Fine lady, forgive me, it is so,’ he said, bowing deeply.

As the train started up, she sent him a smiley face on Snapchat, along with three books in a row. Then the doors beeped once more and the long sleek train started to ease its way out of the old station, gathering speed as she waved.

Her own train, going through the pitch dark, was much slower, stopping everywhere this time, and she found herself, almost from the moment she sat down, falling fast asleep. Stations passed in a blur as she started awake each time, then dozed off again, the train the only thing lit in the empty landscape. By the time they reached the town again, she knew she was in absolutely no fit state to drive back to London that night, and found a cheap Airbnb on her phone, tumbled in gratefully, and fell fast asleep.

The next morning, the snow had settled but the sky was clear and the air was frosty and bright. A nice young farmer brought toast and honey for breakfast from their own farm, and good coffee, and Mirren stretched and felt, oddly, not too disappointed about her failed mission. Or at least, she was sanguine. Time to stop chasing about. She would go back to London, cuddle up to her great-aunt, enjoy every second they had left. She’d read herThe Dark is Rising, that was a good Christmas book. They could enjoy that. And her mother ... well, she’d figure that out too when she got back. But she would endeavour not to be sulky or rise to things. She would try to bring home the true lovely spirit of Christmas. Perhaps they could even read around the fire on Christmas Day. She’d at least mention it to her brothers. Stop Mum fretting toomuch about stupid bread sauce and other things that simply didn’t matter.

She crunched her way through the white early morning streets, enjoying breaking puddle ice with her too-thin boots, pleasingly full of toast and sweet honey, and was happy and quite surprised to see her car, needing its windows scraped but otherwise fixed and untouched, even the swimming costume. In London, it would have been towed days ago, and probably squashed into a cube by now.

She turned the heaters on full blast and sat inside, waiting for the windscreen to fully defrost. Feeling in her pocket, she pulled out the piece of paper from Ramsay.

It was an address back in Scotland – of course it was, she thought to herself. A wild goose chase, this entire thing. She plugged it into her phone.