As shown in season 5, where September(Donald)'s implant is removed, he regains hair, emotions, compassion. But if the the implant makes permanent changes to the brain as is told to Peter when he inserts the same implant into his brain, how does September's brain revert back to normal? Transcript:The human kind mentions this in Act 3 where Walter tells Peter that

"WALTER: Are you also aware that the changes will soon be permanent? And if that happens, there's nothing I can do to get you back."

My question is, If the change is permanent, then how does September transform to Donald?

1 Answer 1


In "The Boy Must Live," when September is describing what happened to him, he says:

As punishment, they removed my device. Now, I’m no longer able to move through time or do the things that I was able to do. They experimented on me. They called it biological reversion. Now, I am no different from you.

That is, turning him back into an ordinary human wasn't just a matter of removing the device; there were also unspecified experiments involved.

Note that Walter says, specifically:

there's nothing I can do to get you back.

If what was done to September was experimental even for the Observers, it seems reasonable to assume that it's totally beyond Walter's capabilities...

  • That was a very concise and accurate answer.. Thanks! So the Observers did possess the technology to revert their own creation.
    – Stark07
    Mar 16, 2014 at 18:16

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