Anna smiled as they headed for Cassie’s Joy. ‘You don’t seem to be in a mess at all.’

Robert MacKenzie gave a snort. ‘Don’t you believe it.’ He stopped and looked back at the cliff, as if contemplating something for a moment. Then he turned to Anna. ‘I’ve got something I want to show you. Come on.’

He took off back across the sand, towards the cliff. Anna followed, only hesitating when she saw him start to climb, fitting the toes of his boots into crevices he seemed to know were there. He reached a wide lip in the rock and turned, crouching to offer her his hand. Anna hesitated.

‘It’s all right,’ said Robert. ‘Trust me. It’s worth it.’

She slipped her hand into his and pushed her toes into the same crevices she had seen him climb. Robert’s hand gripped hers hard and pulled her up. Once she’d found her footing he let her go and turned back towards the cliff face right in front of them.

‘Look,’ he said.

For a moment she was confused. There seemed to be nothing worthy of attention there at all. Then Robert stepped forward, placing one large hand flat against the stone with his thumb and fingers splayed to create a right angle.

‘There. You see?’

Anna peered closer. Inside the space roughly encapsulated by his hand she could make out a series of marks, too deliberate to be caused by erosion or element.

‘They’re petroglyphs,’ said Robert.

‘But – how?’ Anna said, astonished. ‘Who left them there?’

Robert moved out of the way to let her take a closer look. ‘There are examples all along the coast. There’s a cave at Covesea that’s full of them. There aren’t any more here, only these. I’ve never heard anyone else mention them either. I don’t think anyone knows about them but Robbie and me. And now you.’

‘I can’t believe you found them at all,’ Anna said, her eyes tracing the fading shapes. ‘How did you ever see them in the first place?’

Robert was silent for a moment. When Anna looked over her shoulder at him, he was looking away from her, but then he turned back with a faint smile.

‘I didn’t. It was Cass. She always did have eagle eyes. Spotted those that first time she brought me here, while I was down on the beach, shaking wet sand out of my shoes, shouting at her to be careful and wondering if she was ever going to kiss me.’

Anna turned back to the shapes. She reached out, pressing a gentle fingertip to the marks in the cold cliff face, trying to make sense of them. They lined up close beside one another: thin, deep scrapes at angles to each other. Below the first group was a second, and between them a single symbol.