Ten-year-old Ben Tennyson is finally back from his summer vacation... and his life is a mess! Humiliated by his teacher harassed by bullies, grounded by his parents and cursed with a malfunctioning Omnitrix that's vaporising his homework. Ben seizes an opportunity to "get away from it all" by exploring the galaxy with his alien buddy Tetrax. However, he quickly finds himself crashing back to Earth in alien form and unable to turn human again! To make matters worse, Ben soon encounters a deadly Mechamorph Warrior - just like Ben's Upgrade alien, but armed with explosive high-tech armour and a single-minded goal to Destroy All Aliens!