Complex sentence: 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.
Split into simpler sentences: Franklin Storm escaped from prison early in the Fantastic Four's career. 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.