Earth started as a molten wreck orbiting a newborn sun, and this film traces the sequence of accidents that turned it into a place capable of supporting life. It opens with a cloud of interstellar dust and gas collapsing to form the sun and planets, then follows the heat that separated Earth's molten iron core, generating the magnetic field that still deflects the sun's charged particles today. Planetary scientist Robin Canup's supercomputer models reconstruct the collision between early Earth and another planet, a fireball violent enough to melt the surface and throw off the debris that became the moon, locking in the tilt that gives us seasons and tides. At NASA, Michael Zolensky examines a meteorite for evidence that Earth's water arrived from space rather than forming here. In Western Australia's Shark Bay, geologist Martin Van Kranendonk points to stromatolites, bacterial mounds still pumping out oxygen, and a fossilized version nearby considered the oldest fossil on record, the likely source of the breathable atmosphere that eventually made animal life possible.