What really happened in Walter Bishop's Lab in Fringe?

Question

Can anyone tell what really happened in Walter Bishop's lab in Fringe that lead to the hospitalization of Walter in a mental institution?

Note: I have watched whole series.

Answer 1

I believe we never found out much more than that there was a freak fire in his lab that killed a lab assistant (Carla Warren). Walter was initially arrested and charged with manslaughter, but was deemed mentally unfit to stand trial, so he was institutionalized at St. Claire's Hospital in 1991.

However, in the fifth season episode "Black Blotter" (in the new timeline), when Walter takes a dose of LSD to try and remember details about their plan, he hallucinates Carla Warren and this vision of Carla claims that she died in a lab fire in trying to destroy his notebook containing many of his ideas, including the original design for the device to cross between universes.

Answer 2

I cannot fathom how you could have missed this, but in season two newton re-installs 3 pieces of Walter's brain into him using 3 glass jars and some crude electrodes. This results in a completely sane Walter who eventually divulges how to make a doorway safely.

This needed to be done as the alternate universes "Walter" or Walternate as Walter names him wasn't smart enough to be able to figure out how to create a safe way for anything but the shapeshifters to cross over to the crazy Walter's universe. As a side note the story does seem to imply that it was the lack of "Bell" in the other universe that prevents Walternate from coming up with the idea of how to make the doorway; even though it was Walter's idea, he couldn't have come up with it, without Bell being in his life.

Which is the reason why he asked his friend William Bell to remove the information from his brain. You see him begin the surgery by asking walter to think of how he built said door. Later on, Bell in season 3 tells Walter it was actually himself who asked him to remove those parts of his brain. Bell then placed the three parts of walters brain in 3 diffrent people to keep them safe; he knew they would go insane so he placed them in mental asylums before the surgeries. After the lab accident occured Walter decided the knowledge how to make a doorway was too dangerous so he had bell remove the 3 parts of walters brain, it drove him mad and Bell was forced to admit him to an insane asylum as well under the same fake doctors assumed name.