There was a sudden movement behind him, and a crash of something falling. He whirled around in the darkness, every muscle tensing.

The black cat leapt down from its vantage point on a high shelf, landed next to the old nail tin it had knocked over, and darted out through a hole in the planking.

Ben cut across the dark farm and found the gap in the crumbled stone wall leading into Arno’s rambling parkland. He stayed back among the trees, watching the fire crews leave and the police strolling up and down the sides of the gutted villa. He knew he was wasting his time here. It was worthless.

He turned to go, heading back for the gap in the wall, picking his way between the slender tree trunks by moonlight. A cloud passed across the face of the moon, casting the woods in shadow.

He stopped. Lying among the leaves, half-hidden behind a mossy knot of tree roots, a man’s body was lying crumpled and grey on the ground with his arms flung out to the sides.

There was no head on the body.

He waited, perfectly still, watching it until the cloud passed and the moonlight brightened. He went over to it and nudged it with his foot. It wasn’t a body. It was something the clean-up team had missed.

Arno’s tweed jacket. He remembered Leigh dropping it as they ran across the grounds.

He picked it up. It felt cold and damp, and it was empty apart from an oblong shape in the left inside pocket.

He fished it out. It was a slim wallet.

‘Who’s there?’ Her voice sounded frightened in the darkness.

‘Relax,’ he said. ‘It’s me.’ He shut the door of the cabin behind him.

‘Where were you?’

He told her.

‘You went back?’

‘The place has been torched, Leigh. There’s nothing left. But I found something.’ He held up the wallet. ‘It’s Arno’s.’

Leigh sat up in bed as he flipped on a sidelight. He sat on the edge of the bed next to her and she brushed the thick black hair out of her eyes. ‘Where did you find it?’ she asked sleepily.

‘Where you dropped his jacket, in the woods,’ he said. He opened the slim calf-leather wallet and unzipped one of the internal pockets. ‘There’s not much here,’ he said. ‘A library membership card, out of date. A couple of old cinema tickets. Fifteen euros in cash. And this.’ He took out a small slip of paper and showed it to her.

She took it and looked at him quizzically. ‘What’s this?’

‘It’s a receipt.’

‘The Museo Visconti in Milan,’ she said, reading the crumpled print.

‘Ever heard of it?’

She shook her head.

‘This is an acknowledgement of something Arno donated to the museum,’ he said. ‘The receipt doesn’t say what it is, but it’s dated last January, just a few days after Oliver’s death.’

She looked up from the slip of paper. ‘You think-’

‘The letter has gone to Milan? I don’t know,’ he said. ‘We’ll soon find out. Get some sleep. We’re moving on at five.’

The kid had been right about the car. It was old, but it was dependable. It took them to Milan in a little over four hours. On the way they stopped at an autostrada service station where Leigh picked out a headscarf and a pair of wide sunglasses, new jeans and a warm jacket.

The Milan traffic was insane, and it was mid-morning by the time they found the Museo Visconti, an imposing eighteenth-century museum of music in the city suburbs. Its high porticoes overlooked a walled garden away from the street and the traffic rumble.

They went inside and breathed the old museum smell of must and wood polish. The place was almost empty, with just a few middle-aged visitors strolling quietly around the exhibits, talking to each other in subdued voices. The parquet floors were varnished and waxed to a slippery mirror sheen. Classical music played softly in the background. The doorways to each room were flanked by thick velvet curtains. The security guard on patrol looked about eighty.

They walked from room to room under the sweeping gaze of cameras, past displays of period brass instruments and a collection of magnificently ornate antique harps. Ben peered through a doorway into a large gallery space filled with old oil portraits of famous composers. ‘Nothing in here,’ he said. ‘Just a bunch of dead men in powdered wigs.’

‘Philistine,’ Leigh whispered at him.

From the main hall a curved flight of wooden stairs led up to the next floor. Ben went up, and Leigh followed. The creaking stairs took them to a long room whose walls were lined with tall glass cabinets displaying period opera costumes and other exhibits. Leigh stopped at one of them and read the small brass plaque. ‘This is the gown that Caruso wore in his first ever public appearance in 1894,’ she read out. She walked along and stopped at another. ‘Wow. Look. The dress that Maria Callas wore when she sang Norma in Milan in ’57. Incredible. How come I never knew about this place?’

‘Leigh. Please. We’re not here to gape at some old dress. The letter, remember?’

Back in the entrance foyer, the old security guard shook his head. ‘We do not have any letters or documents.’

‘Is there another Museo Visconti?’ Ben asked. He knew what the answer would be.

The old man shook his head again, like a mournful bloodhound. ‘I have been here for fifty years,’ he said. ‘There is only one.’

They walked away.

‘I had a feeling this wouldn’t lead anywhere,’ Leigh said.

‘But Arno donated something. The receipt proves it.’

They walked down a long corridor. On either side were rows of antique violins, violas and cellos behind glass. ‘He was a collector,’ she said. ‘He could have donated anything. A painting, an instrument.’ She pointed at the violins behind the glass. ‘Could have been one of these, for all we know.’

He stopped. ‘We’re idiots.’

‘What?’

‘It’s gone home,’ he said.

She stared at him in confusion.

‘It’s gone home,’ he repeated. ‘Arno said the letter had gone home. It’s gone back to where it came from. He didn’t mean the museum itself. It’s never been here before.’

‘We’re in the wrong place?’

‘Maybe not,’ he said, looking up and down the corridor. ‘We need to find the piano exhibit.’

Understanding dawned on her face. ‘Shit, I think you might be right.’

‘Would you recognize your dad’s old piano if you saw it?’

‘You bet I would.’

Their footsteps rang fast off the parquet as they hurried back up the corridor to find the keyboard instruments section. Through an archway to the side, flanked with red drapes, they found it. The big room was full of old keyboard instruments, pianos, spinets and harpsichords, all highly restored and gleaming. They stood on plinths, cordoned off with DO NOT TOUCH signs on them.

Ben walked in among them. ‘Can you see it anywhere?’ he asked.

‘This is it,’ she said, pointing. She ran over to the old instrument near the window. It was big and ornate. Its woodwork gleamed dully under the museum lights. She circled it. ‘Christ, last time I saw this it was half restored, all stripped down to the bare wood and bits chipped off everywhere. But it’s definitely the one.’

‘You’re sure?’

‘I’d know it anywhere.’

Ben studied the piano carefully, running his eye over the heavily varnished surface, the mother-of-pearl inlays and the gleaming ivory and ebony keys. Over the top of the keyboard, in gold letters, was the maker’s name: Josef Bohm, Vienna. It had three intricately carved legs, two at the front and one holding up the long tail at the back. It was about twelve feet long, solid and heavy. ‘So remind me,’ he said. ‘Which leg was hollow?’

Leigh put her finger to the corner of her mouth, thinking. ‘It was one of the front ones.’

‘Left or right?’

‘Right, I think. No, left.’

Ben leaned over the security cordon, but he couldn’t get close enough to examine the piano properly. He glanced around. There was nobody in sight. He could hear the footsteps of the old security guard pacing through one of the adjacent rooms.