"Give me your immortal soul," was the answer.
"Do you think I am a fool?" asked Twardowski.
"You gave me your promise to go to Rome after seven years."
"That I have already done," said Twardowski, "and I did not promise to stay in Rome."
"Noble deceiver!" exclaimed the Evil One.
"Stupid devil!" cried Twardowski.
Then after a struggle the devil vanished and Twardowski returned home.
For over a year he pored incessantly over his books of magic, until at last he found a formula for warding off death. Then he called his disciple Famulus to him and explained that he was going to test the formula.
"You have always obliged me without question," said Twardowski, "and I expect you to now. Take this knife and thrust it into my heart."
"God forbid!" cried Famulus.