In the grim future of our world, Earth has been ravaged by sentient machines, the human race all but exterminated. Only scattered groups of children have survived by hiding in tunnels to escape the murderous robots that still scour the surface. One day, a scavenging party for one such group happens upon a massive humanoid robot bearing the letters SAM on its armour. Caught by surprise, young Ian is about to be vaporised ... but the machine doesn't shoot...