A self-replicating carbon-based machine created in a laboratory escapes and evolves in the ocean, eventually learning to destroy all life on Earth by breaking down siloxane bonds and converting the planet to silicon dioxide, leaving only one survivor hopeless and alone.
A self-replicating carbon-based machine escaped from a laboratory and evolved into an unstoppable organism that learned to fix carbon from the air, spread through the oceans, and eventually destroyed all life on Earth by cleaving siloxane bonds and converting the planet to silicon dioxide.