After I swim, I watch an osprey hanging in mid-air. If those who came before really do dissolve and dissipate, and if their cells really are all around us, then that bird is held there by Mum and Peter and billions of others of the long-dead. The osprey is kept aloft by absences. Perhaps I am too.

When her husband doesn't answer his phone, Ailsa Piper knows something is wrong. She calls their neighbour, and minutes later, he rings back. 'Oh, Ailsa. I'm so sorry,' he says. Five words to change a life.

Wanting to flee her shattered world in Melbourne, Ailsa migrates north to Sydney. She makes a nest. She learns to swim. She walks the harbour cliffs to the lighthouse, meeting the locals: winter swimmers and shoreline philosophers.

But we never leave our past behind. Ailsa is drawn back south, and even further back, to the west's aqua waters ...