On her way home from school Alex Mack is practically hit by a truck. The truck is carrying a top-secret chemical and spills it on Alex. Alex learns later that she has magical powers and shares this secret with her sister, Annie, and best friend, Raymond.

Alex and Raymond are continually harassed by upperclassmen Jessica and Ellen. One afternoon Jessica trips Alex in the school cafeteria as Alex carries a tray full of food. A food fight ensues and Vice Principal Heller assigns Alex, Raymond, Jessica and Ellen to clean up the cafeteria every afternoon. Both sets of friends blame each other for the trouble, and they agree to take up Raymond's challenge of two-on-two on the basketball court. The stakes: the losers have to admit responsibility to Heller and clean up the cafeteria by themselves.

The big dance is just around the corner and Alex still hasn't been asked by the only person she cares to go with. Everybody knows she dreams of going with Scott, but he's not the one hounding her for a date. Jerry, an obnoxious, insensitive and persistent ninth-grader is relentless in his pursuit of her. He won't take no for an answer, but Alex continues to put him off.