I frowned. ‘But it doesn’t go anywhere.’

‘Of course it does.’ He pointed off to one side, into darkness. ‘Come and see.’

I wasn’t really going underground, I reassured myself. The sky was still above me, calmly blue. But when I reached the bottom step the air was dank, and the only thing that kept me from bolting right back up the steps was the fact that I’d have flattened Paul in the process. He leaned in now, behind me, looking where Simon had pointed. One had to focus past the iron bars to see the dimly stretching corridors beyond. ‘You’re right,’ he told his brother. ‘This is neat. Where does it lead?’

Simon consulted the hand-sketched map he held. ‘I’m not sure. The woman at the gate said there are tunnels all over the place, not just under the château but all around Chinon. I think she said Resistance fighters used them in the war.’

It was easy to imagine that. Easier still to imagine the echo of earlier times. I could almost see the torchlight casting shadows on the arched stone walls, and hear far off the furtive rustle of a velvet gown against the eerie silence. I wondered if this was the tunnel Isabelle had passed through, on her way to hide her treasure …

I was so deep in my imaginings that the sound, when it came, caught me unawares. A sound quite real and not imagined: the quiet closing of a door, somewhere in the dark and stretching shadows.

I cleared my throat. ‘Did you hear that?’

‘Hear what?’ Both brothers looked at me blankly.

‘It sounded like a door.’

Paul tipped his head and listened, but the dusty walls stayed silent. ‘Maybe the château workers use the tunnels,’ he suggested, ‘to get around the place. Or for storage.’

It seemed logical enough, I thought. But I felt a good deal better when we’d clambered up to ground level again, up in the sunshine where the breeze could blow the shivers from my skin.

‘Oh, hey,’ said Simon, looking at his map, ‘I think that might have been the tunnel that goes to the vineyard.’ Brow furrowed, he followed the tracing on the map and tried to match it with his own steps, so deep in concentration that he didn’t seem to notice when he left the grass and walked onto a broad paved circle that jutted out from the château walls. It might have been a tower once, or some such other fortification, but time had worn it level with the lawn. And Simon might have kept on walking, clear off its edge, had Paul not whistled sharply.

‘What?’ Simon raised his head, enquiring. He stopped two inches from the railing and leaned over, with a nod. ‘Yeah, that’s where it leads, all right. If Isabelle hid her treasure there,’ he told me, as we joined him at the railing, ‘your cousin can kiss it goodbye.’

Below us ran the road that had brought me into Chinon yesterday, now busy with a blur of passing traffic. And on the other side of the road was the most incredible estate I’d ever seen. It was a vineyard, a huge and wealthy vineyard – so huge, in fact, that the rows of dark green vines rose up the rolling slope to the horizon and beyond, protected by a tall unbroken boundary wall that ran along the road. Well, almost unbroken, I corrected myself. There was a gate, a great iron thing that would have suited Buckingham Palace, and from the gate a broad drive swept imperiously up the hill to meet a Grecian mansion, gleaming white.

Above our heads a cloud raced underneath the sun and sent a shadow swiftly up the deeply furrowed hill, as the shadow of a hawk might chase its prey across a trembling field.

Paul understood my awe. ‘The Clos des Cloches. It’s really something, isn’t it? I’m told they make the best wine in Chinon.’

The Clos des Cloches – the vineyard of the bells, I translated in my own mind. ‘It’s beautiful.’

Simon shifted closer. ‘Martine says they give tours in the summer, and wine-tastings, but it’s out of season now. Everyone’s too busy with the harvest.’ Elbows on the railing, he hung forward, heedless of the dizzying drop. ‘Hey, look,’ he said, ‘there’s Neil.’

I looked. The bright gleam of Neil Grantham’s hair made him easy to spot on the narrow path beneath us, by the road. Two other men were with him, and a woman with short dark hair. I couldn’t see their faces from that angle, but Simon gave a low whistle.

‘Damn Neil,’ he said, good-naturedly. ‘He always beats my time.’

Paul smiled. ‘That,’ he told me, with a downwards nod at the dark-haired woman, ‘is Martine Muret.’

Martine Muret. I frowned. Oh, right … the woman Garland had been gossiping about in the hotel bar yesterday afternoon. The one whose former husband had just died … what, three days ago? I watched her now lean close to Neil, her hand possessive on his arm. She had a quick recovery time, I decided drily.

Simon shouted down and waved, and I pulled myself up quickly, taking a step back from the railing. ‘Listen, it must be nearly lunchtime. I’d better go back down, in case my cousin’s come.’

‘Are you sure?’ Simon turned around, distracted. ‘Because there’s a Joan of Arc museum in the Clock Tower, if you’d like to …’

I hastily assured him I’d seen plenty for one day, and it was always best to leave something for the next time …

‘Well, it is your first day,’ Simon conceded with a shrug. ‘We probably shouldn’t wear you out.’ He checked his watch. ‘And you’re right, it is lunchtime. Hey, Paul, let’s go ask Neil and Martine if they want to try that Chinese place across the river.’