Mighty Mouse, the mightiest mouse of them all, swoops down from the skies to rescue Pearl Pureheart from death on the roller-coaster rails at the amusement park. Oil Can Harry, the meanest villain of them all, is cursing at being foiled once again by the super-hero, and even manages to get the upper-hand on Mighty and put Polly Pureheart again in the path of peril, but you can't keep a good mouse down and, once again, here comes Mighty Mouse to the rescue.