A clueless optimist ruins a perfectly good hell.
Pity poor Lucifer. He rules hell with a vice grip. Demons and damned scatter at the sound of his foot steps. The Supreme Butt In hasn't pestered him in eons. Lucifer's future looks perfect, pitch black, until an administrative error sticks him with an innocent soul—an overweight optimist who calls himself Pilgrim and who believes he must be in hell to do good.
Lucifer never considers sending him back. He orders his subordinates to torture, degrade and humiliate Pilgrim until he promises to become evil if only it will ease the pain. Unfortunately, Pilgrim makes the best of the worst possible experiences. Always polite and well-mannered, he makes Pollyanna seem like a prophet of doom. Even worse, the damned start catching on, and set about making hell into the most enjoyable place of everlasting torment they can.
Lucifer can't let Pilgrim continue to wreak happiness, but he can't send him back untainted, either. When God arrives with a deadline for Pilgrim's return, he enlists fellow fallen angels Screwtape, Azazel and the gender morphing Mephistopheles in a plot to corrupt Pilgrim's soul before the deadline expires.