A 14-year-old boy named Billy Batson is granted the powers of six ancient heroes by a dying wizard, which he activates by saying the wizard's name, "Shazam!" Upon doing so, he is transformed by a magic lightning bolt into an adult superhero. Each of the ancient heroes' initials are represented by the letters in the word: the wisdom of Solomon, the strength of Hercules, the stamina of Atlas, the power of Zeus, the courage of Achilles, and the speed of Mercury.
While Billy at first revels in the joy of being a hero - albeit one who still has a teenager's mind - he is forced into serious action in order to battle the evil Doctor Sivana. On Billy's side is his foster brother and best friend Freddy Freeman, a superhero enthusiast who helps both train Billy and keep Billy's secret.