Yeah, I'm on a BIG Big Hero 6 kick after seeing the movie on 11/16/14. It is one of my new all-time favorite movies Disney has made! And it also made me cry! Which rarely ever happens to me during a movie!
So anyway, unless you have seen the movie, some of these plot ideas might spoil a few things for you so I would recommend to see the movie first before reading them!
1) Tadashi survives the fire but he is severely injured from smoke inhalation and one night when he is recovering he has an asthma attack because his lungs were damaged when his next project was working on starts smoking up his lab and he has a panic attack because he thinks he’s in the fire again and Hiro has to calm him down.
2) Hiro runs into save Tadashi, he spots the professor using his microbots but manages to get Tadashi to safety. As Tadashi recovers Hiro and the team try to find out why the professor would do such a thing while Baymax takes care of Tadashi.