War Horse author, Michael Morpurgo has written a new book marking 100 years since the start of the First World War.
He says 'Listen to the Moon', which focuses on a young boy Alfie and his fisherman dad, was inspired by a story from his own family.
They find a girl alone on an island in the Scillies - a group of islands off the south western tip of the Cornish coast.
She's hurt, lost, and with no memory of who she is or how she arrived there.
Michael said: "There was once in our family a medal, commemorating the sinking of a ship called the Lusitania in May 1915. I learned it had been torpedoed by a German U Boat, in the south of Ireland."
He added: "I discovered that three hours after it sank, the grand piano from the dining room of this luxurious cruise liner was found floating on the sea, with a child still hanging on."