Bí ẩn phòng giam số 13

Professor Augustus S. F. X. Van Dusen had a very long name. Over the years he had also collected a great many letters to put after it, from universities all over the world. He was a doctor of philosophy, a doctor of law, a doctor of medicine and several other things. Even he could not remember them all.

He looked as strange as his name. He was thin, and his shoulders were bent from years of study. His face was pale, because he almost never went outside. Behind his thick glasses, his small, watery blue eyes were always half closed, like the eyes of a man who studies very small things. But the most surprising thing about him was his head. His forehead was enormously high and wide, and on top of it grew a thick mass of yellow hair. He wore a hat of size number eight.

For about thirty-five years, the professor had worked to prove one simple idea. Two and two always make four, not sometimes, but all the time. He believed that every problem had an answer, and that the human mind could find it.