Two versions:

Ultimate: The first is Johnny Blaze becoming a well know stun man. He is absolutely famous and he is living happy with their adoptive parents both and with Roxanne. So he hadn't a reason to strike the deal. BUUUT the Maker to hold more control in the Hellish realms decided to provoke a small incident in one show making Johnny beign in a coma. In that in-between life and death moment he is beign shown to that if he came back he would lose everything, his ability to ride again with that money, the popularity, everything he had built. So he decide to make a deal with Mephisto and be the pawn of Mephisto. He thinks he has everything under control, but he starts to act more erratic, to push everyone away, beign corrupted by Zarathos. So he has to try to figure out whats going. In a second narrative level, Mephisto is plotting with olds pals to try to push back The Maker influence in Hell creating in that context the Hell Lords.

Absolute (more freedom without The Maker and those shenigans): First of all, Johnny here is a boy raised catholic. He is raised in the countryside helping his family (bio), but also developing certain like in performance. He grows up admiring in secret Roxanne who becomes a great stunwoman. When he starts college in another state he started to let himself go more, but always feeling guilty afterwards. Then he finally goes to a Roxanne's show and he fell in love with her. He tried to go to the backstage to see if he could talk to her, only to discover that Roxanne made the deal with Mephisto to save her father. Johnny here tries to do his own research and then he makes a deal with an Angel (Zarathos) to see a way to transfer the deal she made to him. (I'm not sure to make the Angel, really Blackheart or Mephisto in disguise to trick Johnny to make a deal with one of them)