Nothing is impossible for Geronimo Superstilton!He helps watch over Muskrat City, ready to fight evil at all costs. He is strong... he is invincible... he is fearless! (Well, almost.) He is one of the Heromice!Now that the terrible Tony Sludge has escaped from prison, it's up to Geronimo Superstilton and the Heromice to defend Muskrat City from the notorious Sewer Rats and stop an enormouse blackout! Will our heroes be able to defeat their enemies without risking their fur?