Deep in the fiery underworld, Satan prepares to step down as the ruler of Hell after ten thousand years of service. He gathers his three adult sons to choose a successor. The eldest, Cassius, is ruthless and ambitious, while the middle son, Peter, is pompous and overly
intellectual. The youngest, Nicky, is a gentle, sweet-natured misfit with a speech impediment and a disfigured jaw, the result of a childhood incident involving a billiard ball and his brother Cassius. Much to the horror of Cassius and Peter, Satan decides to extend his reign for another ten thousand years, refusing to hand over the throne to such ill-suited heirs.Furious and desperate for power, Cassius and Peter hatch a rebellious plot. By opening a magical portal, they freeze the gates of Hell, preventing any new souls from entering and causing Satan to slowly disintegrate into ash. To save his father and restore balance, Nicky is reluctantly sent up to the chaotic and bizarre realm of New York City to capture his renegade brothers using a mystical empty silver flask.Upon arriving in the mortal world, Nicky is completely out of his depth. He is repeatedly subjected to brutal physical trauma—struck by cars, beaten with baseball bats, and crushed by heavy objects—only to miraculously regenerate due to his demonic resilience. Despite his grotesque appearance and naive demeanor, Nicky unexpectedly finds an ally in a kind-hearted human woman named Valerie, who looks past his bizarre traits and falls in love with his pure soul. He also befriends a talking, smoking bulldog and a trio of heavy metal fans who recognize his inherent goodness.Meanwhile, Cassius and Peter wreak havoc on Earth, possessing humans and gaining immense power. Cassius eventually tracks Nicky down, easily overpowering him and trapping him in the magical flask, intending to rule Hell unopposed. However, with the help of his new friends and a timely
intervention from his mother, an angel named Holly, Nicky escapes his prison.Returning to Hell with the flask, Nicky confronts Cassius in an epic showdown. Utilizing his newly discovered courage and cleverness, Nicky manages to trap both Cassius and Peter inside the flask, effectively saving the underworld. As a reward for his bravery, Satan finally grants Nicky his greatest wish: a repaired jaw, normal speech, and the ability to return to Earth to live happily with Valerie. Nicky bids farewell to his demonic family, embracing his new life as a hero who successfully bridged the gap between the fiery depths of Hell and the bright lights of the human world.