"When music researcher Phineas Fox is asked to verify the contents of an old scrapbook, rescued from the site of the historic Chopin Library in Warsaw, he is initially sceptical. But he soon discovers an intriguing link between the Library and an infamous piece of music known as the Dark Cadence. Legend has it that the Dark Cadence was only performed at a traitor's execution - and it has never been written down. It is believed to have last been played...