The story of Captain Marvel starts with Billy Batson, a 12 year old homeless newsboy, who is led by a mysterious stranger to a secret subway tunnel. An odd subway car with no visible driver takes them to an underground tunnel with seven statues depicting the Seven Deadly Enemies of Man (Pride, Envy, Greed, Hatred, Selfishness, Laziness and Injustice): the lair of the wizard Shazam. The wizard shows that he has observed the hardship of Billy's life, and grants him the power to become the adult superhero Captain Marvel, just before a stone suspended above Shazam's head crushes him. His ghost says he will give advice when a brazier is lighted.
In order to transform into Captain Marvel, Billy must speak the wizard's name, an acronym for the six legendary figures who agreed to grant aspects of themselves to a willing subject: 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. Speaking the word SHAZAM! produces a bolt of magic lightning which transforms Billy into Captain Marvel. Speaking the word again reverses the transformation with another bolt of lightning. (wikipedia)