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! Flood mission. Muskrat City is under attack again. The Sewer Rats have created a weather-changing device that unleashes hug storms, which will likely flood the entire city. The rodents of Muskrat City have one hope: The Heromice.