As he spoke, something fluttered from the darkness and darted towards us. I gasped and ducked, covering my head with my arms and Joe ducked too and then laughed.

‘Oh Jesus, it’s just a sparrow!’ He stood straight. ‘Poor little sod must have been trapped.’

I smiled, but inside my heart was pounding.

Because of the shutters, the interior of the villa was dark as a cave, but behind us sunbeams spread through the open door across the ornate tiles of the hallway floor. I stepped slowly over the ridge of salt into my own shadow. Despite the musty smell, the floor was clean, save a feather or two. A giant, crystal chandelier, draped with cobwebs, hung high above us, filling in the dome of the ceiling, glass droplets trapping the reflection of light from the floor tiles and sending them out again; twinkling the effect of an elaborate disco ball.

Joe tried the light switch, but nothing happened.

Slowly, my eyes adjusted to the gloom. Two large items of furniture stood in the hallway, both covered with dust sheets. To one side of the door was an arch shaped alcove with candleholders on either side. The hallway opened into a long, dark room to its right and, to the left, stairs led upwards. Three other doors along its length were closed. A small brown object, like a fossilised croissant, lay at the foot of the stairs.

Joe picked the thing up and tossed it outside.

‘What was it?’ I asked.

‘Nothing.’

‘Joe?’

‘It was a sheep’s horn.’

‘A sheep’s horn?’

‘It’s to keep the villa safe. Don’t worry about it.’

I gave a small laugh. ‘A whole sack of salt and a sheep’s horn. That’s a lot of precautions.’

‘When you live on an island that’s been invaded so many times, you’re bound to be worried about people breaking in to your property,’ said Joe.

But that wasn’t the reason for the salt and the horn and we both knew it. The villa had been made secure already; the planks over the doors and shutters would keep vandals and burglars out. These objects were to protect against a different kind of intruder.

Joe switched on the torch on his phone, directed the light into the alcove and moved the beam around, into every corner.

‘It’s not there,’ he said.

‘What isn’t?’

‘The painting, the Madonna del Mare.’

‘The one your mother was worried about?’

He nodded and ran the flat of his hand along the ledge of the alcove. There was a brighter patch in the paintwork, where a picture had hung for many years.

‘What does it look like?’ I asked.