Jefferson isn't dead. He would be, save for Gideon–Martin can literally feel that in his bones–but for now he's breathing still.
And there're so many things Martin needs to tell Jefferson, now that he's still. Like that he shouldn't take such risks. That Martin is sorry for making them come, yet will never regret choosing to stay. That Martin knows he's selfish, but he will not risk yet another life to preserve his own. That Jefferson will be his last Firestorm.
When Jefferson's eyes open, the only words Martin can find are, "Oh, my dear boy, welcome back."