Franklin Storm escaped from prison early in the Fantastic Four's career, and when he learned that Susan had been seriously injured while escaping from the Mole Man's lair, he came out of hiding and operated on her, saving her life.
Franklin Storm escaped from prison early in the Fantastic Four's career. He came out of hiding. He operated on her. He was saving her life. Susan had been seriously injured while escaping from the Mole Man's lair. He learned this.