Six-year-old Poppy is an orphan everyone bullies. After her parents die saving others, she lives alone in a rundown shack. On Christmas Eve, she accidentally sends her wish letter to Satan—because “Santa” and “Satan” look far too much alike.
Satan sends his three-headed hellhound, Cerberus, to protect her—disguised as a puppy, two heads removed, a red bow tied around its neck, and a threat ringing in its ears: take care of my little believer. Cerberus becomes “Pippy” to Poppy. He drives off a vagrant who breaks into her home. Poppy discovers she can hear him talk—and is overjoyed that she finally has family.
But the school bullying doesn’t stop. Tyler steals her new coat and stomps on the apple she saved for Pippy. Satan comes to heal her scrapes, his heart aching for the little girl without him even realizing it. When he sees her bullied again, he can’t stand it. He descends in person as a giant black shadow and sends the cruel kids flying—and breaks Hell’s law doing it. Black lightning strikes him, leaving him badly wounded.
Poppy seems to sense that someone saved her. She shovels snow, gathers apples, drags home a crooked little Christmas tree, and records a whispered message for the grown-up who protected her, sending it back with Cerberus. Alone in his great hall, Satan presses the recording doll again and again, listening to the child’s voice, and feels his heart go soft.
Then Tyler’s mother reports Poppy as an orphan, and the orphanage comes to take her away. Ignoring his unhealed wounds, Satan appears as “Lucifer Morningstar” and adopts Poppy as his daughter. Two hearts draw closer, each saving the other.
On Christmas Day, Poppy wishes to see her parents one last time. Lucifer storms Heaven, fighting the angels to bring their souls back to her. Scorched by holy light, his body covered in wounds, he still shields her parents’ souls and carries them home. In a dream, Poppy says goodbye to her mother and father. Her mother tells her, “He brought us to you.