Willow was driving like a maniac down the narrow roads. The fog had settled again and visibility was poor. Occasionally house lights would swoop at them out of the gloom, or headlights would appear straight ahead of them so that she had to swerve onto the verge. But Perez didn’t ask her to slow down. Like Willow, he was desperate to get back to Unst. He couldn’t bear the idea that they might have to wait an hour for the last ferry. He sensed that they’d soon reach the end of the investigation and they needed to be on the most northerly island of the archipelago before there was another tragedy.

Sandy was looking out for them. It was nine o’clock. As they opened the main door to the Springfield House the long-case clock in the hall chimed the hour. He had the light on in the kitchen and had been peering out at the shadowy courtyard to check that the car he’d heard belonged to them. He’d looked like an anxious child, left alone in the house for the first time, waiting for his parents to return.

‘I need tea.’ Willow slumped in one of the chairs and took off her shoes. Perez saw that there was a small hole in the toe of her hand-knitted sock.

Sandy switched on the kettle. ‘So, did you find Monica?’

Perez explained about the empty bungalow and the visit to the gallery.

‘So you think she was away before the killings?’ Sandy said. ‘I can’t confirm that. Nobody from North-Link or Flybe will be available until seven tomorrow morning.’

‘She can’t have left on the Friday.’ Willow had her hands cupped round the mug of tea and Perez thought she looked exhausted. ‘She saw Eleanor’s body.’ She explained to Sandy that they’d seen a sketch of the dead Eleanor in Monica’s house.

‘That’s not necessarily true, is it?’ Perez had been thinking about that. ‘She didn’t need to see Eleanor’s body to make the drawing. She just needed to know that it would be there.’

‘The murderer confided in her beforehand, you mean?’ Willow looked up sharply. ‘If you’ve got a theory about this, Jimmy Perez, now’s the time to share it.’

Perez hesitated. He wasn’t sure what to say. His phone started to ring and he took it out of his pocket. Cilla, Eleanor’s mother. He’d saved her number when he was in London.

‘Inspector Perez.’ She sounded very old and her voice was slurred. She’d been drinking. ‘I’ve been thinking about our conversation.’

‘Yes?’