<p>A young Cambridge University professor, Horace Holly, is visited by a colleague, Vincey, who reveals that he will soon die. Vincey proceeds to tell Holly a fantastical tale of his family heritage. He charges Holly with the task of raising his young son, Leo (whom he has never seen) and gives Holly a locked iron box, with instructions that it is not to be opened until Leo turns 25. Holly agrees, and indeed Vincey is found dead the next day. Hol...