Sam and Mark continue their search to find the world's next great superhero. 10 superheroes remain in the lair. The superheroes attempt to foil Dr Dark's latest evil plan: to contaminate the city with radioactive waste. The superheroes are forced to roll their sleeves up and get their hands dirty as they attempt to retrieve 10 radioactive canisters from a skip at the city dump. But the clock is ticking as the canisters have been programmed to detonate. Will the superheroes be able to remain calm under pressure? Will they work well as a team? And with only one superhero entering the skip at a time, will they all get a chance to save the city? As if saving the city was not enough, Sam and Mark set the superheroes the small task of saving the world. But this mission has a hidden test; it is actually designed to test the superheroes' observation skills. Will any of the superheroes stop to properly assess the situation and save the world? And with the superheroes working in pairs, their teamwork is put to the test once again. Three more superheroes are called forward to face the Power Down. Plus, Sam and Mark make a surprise announcement.