One of the most memorable moments from The Hunger Games' four films comes halfway through the third film, Mockingjay: Part 1. Stuck in District 13 with Gale and the other rebels, Katniss Everdeen is asked to sing something for the mockingjays around them to imitate. She responds by singing a snatch of an old folk song from District 12, called "The Hanging Tree." The song goes on to become the rebel's theme song. Now, in the new novel, The Ballad of Songbirds and Snakes, the origin of The Hunger Games' "Hanging Tree" song is revealed. Warning: Spoilers for The Ballad of Songbirds and Snakes follow.
In the novel, Coriolanus Snow is assigned as the student mentor to the girl from District 12, Lucy Gray. The two of them conspire to find ways to give her an advantage in the arena. For instance, Snow sneaks her food so she's not half-starved when the games begin, and gives her his mother's compact, which she fills with rat poison as a way to off her competitors. Snow also lucks out and sees Dr. Gaul, the Gamesmaster, preparing to release weaponized snakes into the arena. He slips a handkerchief Lucy used into the cage, so the snakes recognize her smell and befriend her instead of attacking.
These measures pay off, and Lucy wins. But when they are uncovered, Snow is banished to District 12 for cheating, forced to become a Peacekeeper. Since Lucy Gray is also sent home after her win, he doesn't mind; the two are in love and happy to be free together. But it's not long before trouble starts. A rebel is charged with killing three men, and Snow must guard the crowds as the man is hanged.
The man's name is Arlo, and he is swung from the District's hanging tree. Before the platform gives way, he looks out into the crowd and sees a woman crying. Her name is Lil, and Peacekeepers are closing in on her, recognizing her as his lover and accomplice. From his platform, Arlo screams to her to run. "Run! Run Lil, ru..."
As he falls, his neck breaks, cutting off his cries, even as the mockingjays take them up.
Snow hates the creepy birds, calling them unnatural and spooky. He also blames the crowd for being unruly and causing such a scene. But Lucy Gray is deeply affected by what they witnessed. A couple of days later, when he goes to meet her in her meadow, she's writing a song about what she saw.
Are you, are you/Coming to the tree...
By the time Katniss learns the song decades later, it's become a traditional song of rebellion. (Lucy disappears by the book's end, forgotten.) She has no idea the song she inspires the rebels to sing was written by the girl President Snow once loved. She has no idea he once stood in a meadow of District 12 as Lucy tested different melodies. Katniss never knows she brings the world full circle with one song.