This was by far the best moment from last night's Fringe episode — the acid-tripping Walter Bishop goes into a Terry Gilliam-inspired Monty Python animated fantasy, complete with giant foot. Especially love Walter riding on Gene, and his three companions becoming weird creatures.

In general, "Black Blotter" felt like a pretty run-of-the-mill episode, in which Walter confronts his past hubris once again, and the "plan to defeat the Observers" storyline inches forward. But there were a few neat moments, like the one above. Spoilers ahead...

In "Black Blotter," Walter drops acid in an effort to remember the plan to defeat the Observers that was wiped from his mind in the season opener. He's desperate to remember the plan and put it into effect, before he finishes turning back into the man he was before — the man who broke the multiverse and played God, and all that.

Unfortunately, while Walter is tripping balls, the radio the gang brought from the pocket universe suddenly starts picking up a coded signal, apparently indicating where to find the Child Observer who was taken from there. The gang is forced to go hunting for the source of the signal while also coping with a Walter who's hallucinating confrontations with his dead former lab assistant and a young Nina Sharp, plus finding an old notebook detailing his genius plans, like how to make a potato-powered generator.

In the end, they find the Observer Child, who hasn't aged a day, and all is well — except that Walter is tormented by replaying, over and over, his arrogance and senseless destructiveness.

Oh, and meanwhile, Peter is basically fine except for some headaches and insomnia. He's gained a new appreciation for how lucky he is to have Olivia in his life, given how much of a jerkface he keeps being to her. But he doesn't appear — at least for now — to have any lasting ill effects from his brain implant.

The main point of the episode seems to be introducing the notion that Walter actually has a split personality and Evil Walter actually has a totally separate existence from Nice Walter. Evil Walter actually got dressed and started heading out of the lab recently, before Nice Walter was able to reassert control. But Nice Walter still has no idea what Evil Walter was up to — except that when he's tripping, he gets an inkling that Evil Walter was planning to go meet the Observers and show them the fruits of his genius so they'd celebrate his massive brain. As plans go, it seems kind of half-baked.

So is Evil Walter a separate personality, rather than just an aspect of Walter's personality? Certainly the first time we saw Walter with the pieces of his brain put back in, in "Grey Matters," the result seemed to be a more callous, snarling version of Walter. And with the brain pieces put back in, Walter had knowledge that he'd previously lacked — particularly the knowledge of how to create a doorway to the Other Side. But at the same time, it seems like a bit of a leap from "Evil Walter has more knowledge and a more ruthless attitude" to "Walter has a split personality, where he can't remember what his evil side has done." Of course, all of this is in Walter's head, so if he believes it's possible, then it is possible.

In any case, until this week, Walter's quest to rid himself of those extra brain pieces has seemed quixotic, if not counter-productive — it's entirely likely that Evil Walter might be more effective in fighting the Observers than regular Walter. But now we're getting introduced to the idea that Evil Walter might be a collaborator, and might just choose to help the Observers instead of standing with his friends. Which, again, doesn't seem like a great plan.

So Peter's stint as a Fauxserver is being swept, more or less, under the rug, and he's being welcomed back into the fold — but meanwhile, Walter is being inexorably carried away by his bad side. Given that it seems more and more likely that the key to defeating the Observers will turn out to be human emotion, I'm guessing we'll be seeing Walter almost lose his humanity before regaining it just at the final moment.