The Moon sits so close and so familiar that almost nobody questions it, but this film asks what Earth would actually be like without it. Space scientist Maggie Aderin-Pocock leads the investigation, moving from tidal pools to computer simulations to work out how much of life on Earth depends on the Moon's gravity and its stabilizing pull on our planet's tilt. Interviews with astronomers and geologists lay out the leading theory of the Moon's violent origin, a Mars-sized body colliding with the young Earth, and trace what that impact set in motion: the length of our day, the rhythm of the tides, and a climate steady enough for complex life to evolve. The film also looks at other worlds in the solar system to test the idea by comparison, asking whether a planet without a large moon could ever produce anything like Earth's biosphere. It treats the Moon less as scenery and more as a piece of planetary machinery whose absence would rewrite the rules for everything below it.