“Well,” said I, “I can make nothing of it.” The Professor stood up. “I must go back to Amsterdam tonight,” he said. “There are books and things there which I want. You must remain here all the night, and you must not let your sight pass from her.”

“Shall I have a nurse?” I asked.

“We are the best nurses, you and I. You keep watch all night; see that she is well fed, and that nothing disturbs her. You must not sleep all the night. Later on we can sleep, you and I. I shall be back as soon as possible. And then we may begin.”

“May begin?” I said. “What on earth do you mean?”