Guilt and Gingerbread — Leon Garfield

'When you take out the heart of gold, you must put something back in its place. Otherwise our princess would die.'

Giorgio, a poor student, sets out on a journey to win the heart of Princess Charlotte of Oberweselberg. On the way an old woman promises he shall have the princess - but for a price. Giorgio must bring her the princess's golden heart. Can he do the wicked deed which will possess for him the fortune he desires?