Overhead the clouds began to thicken and the sun disappeared. Against the jagged back wall of the church, in what looked like a fire pit, somebody had laid a bouquet of dried flowers, or herbs. Zoe picked it up.

‘They had real independence,’ Eva said. She reached out to take the flowers. ‘Imagine the freedom,’ she went on, as her foot prodded the fire pit. ‘In that age, the seventh, eighth centuries. They had their own community, with its own rules. They had a library, they collected books. They wrote books, illustrated them. They grew vegetables, kept bees. Some of the women were high-born, some not. I imagine them as a community with a wellspring of values, a sisterhood.’

‘But they were controlled by the Pope, or bishops, or someone,’ Zoe said.

‘They did their own things on these islands. I don’t think anyone would have bothered them much. The motherhouse was the abbey in Ayrness.’

‘Where did the nuns go? What happened to them?’ Zoe asked.

‘When the abbey in Ayrness became Benedictine,’ Eva said, ‘the nuns were evicted, and were sent here. They hung on for a few more centuries. But then the bubonic plague happened. At first, the islands were protected from the plague by the sea. They didn’t need anything from outside. Until a monk from one of the mainland monasteries came to the convent library, looking for ancient manuscripts. He was probably a merchant of some kind. Almost all the nuns died.’

Eva’s face, framed by its wild hair, had seemed almost youthful, moments earlier; now Zoe saw how tired she was.

They walked towards the clifftop. Out at sea, a green and yellow sailing boat was cutting slowly through the water. Zoe took Eva’s binoculars and looked across the horizon, up at the storm petrels and Arctic terns, and down at the boat.

‘It’s Inga,’ she said after a moment. ‘It’s Inga in the boat, with Mx Thompson.’

‘Well now,’ said Eva, taking the binoculars from her. She watched the boat. Then she said, sounding pleased, ‘She’s done it. She’s got really good at sailing.’

Zoe slipped her hand into Eva’s pocket and took out the wine gums.

‘When are we going over to Cwen next? It’s our time. I know it.’

The first time the girl is brought over to her island, she is only a child.

She is brought over by the woman at the summer solstice, when the skies are suffused with light. Cwen watches them, and knows they are grandmother and granddaughter. Too old to be her mother, even for these times. She watches the love flow between them, back and forth, meeting and turning and overturning, like tides around her island.