The storm had thrown half the ocean onto the beach. Lena picked her way through the mess of kelp and driftwood, her boots squelching, scanning the sand the way she always did after a big blow. Her collection at home already held three fishing floats, a brass button and the skull of a seabird, but she was always hoping for something better.

She nearly missed it. Wedged beneath a tangle of weed was a green glass bottle, its neck sealed with wax. Inside, rolled tight, was a sheet of yellowed paper.

It took ten minutes and a butter knife at the kitchen table to get the wax off. Lena eased the paper out and unrolled it carefully. The handwriting was loopy and uneven, the kind that belonged to someone young.

'To whoever finds this,' it read. 'My name is Rosa and I am eleven years old. I am throwing this off the jetty at Port Lincoln on the last day of the summer holidays. I want to know how far it goes. If you find it, please write and tell me where you are. Rosa Petrakis, 14 Harbour Street, Port Lincoln. 2 February 1998.'

Lena read it twice. Then she read the address a third time and felt something cold slide down her back.

Port Lincoln was three hundred kilometres away. The bottle had been at sea for nearly thirty years. And 14 Harbour Street — she knew that address. She had written it on the top of her school forms every year since kindergarten. It was her nan's house. The house where Mum had grown up.

'Mum,' she said, walking into the lounge room with the paper held out in front of her like a torch. 'What was your name before you married Dad?'

Her mother looked up from her laptop. 'Petrakis. Why?'

Lena didn't answer. She just handed her the note.

Her mother read it once, and then she laughed, and then she put her hand over her mouth and stopped laughing. 'I remember this,' she whispered. 'I remember doing this. Nan said it would wash up by dinner time.'

'It went three hundred kilometres,' said Lena. 'And it took twenty-eight years. And it came to me.'

Her mother looked at her for a long moment. 'Well,' she said at last, 'I suppose you'd better write back.'