Book excerpt: An Agatha Christie short story from the collection The Golden Ball and Other Stories. A young Englishman visiting Cornwall finds himself delving into the legend of a Belgian nun who is living as a refugee in the village. Possessed of supernatural powers, she is said to have caused her entire convent to explode when it was occupied by invading German soldiers during World War I. Sister Angelique was the only survivor. Could such a tall tale possibly be true?