Alex Mack is an ordinary teenage girl, living with her parents and older sister. While walking home after her first day of junior high school, she is nearly hit by a truck from a chemical plant, and during the incident, she is drenched with a top-secret chemical called GC-161. She soon discovers that it gave her strange powers. These include telekinesis, the ability to zap bolts of electricity from her fingers, and the capacity to morph into a mobile puddle of water.