Watch full movie online. Re-enactment of the famous May 31, 1889 Johnstown, Pennsylvania flood where the dam broke and flooded out an entire town! In this version, the town is occupied by mice and dogs. But Mighty Mouse comes to the rescue after drinking a bottle of "Atomic Energy." He reverses the flood waters and puts everything back where it was. And in this cartoon, he uses magic lightning bolts coming off his hands like Merlin the Magician!