The shortwave radio from the pocket universe starts beeping one night out of the blue. Astrid is the first one to hear it, so she looks for Walter to decode the pattern of beeps. Unfortunately, he's in the middle of an acid trip and existing mostly in a world of his own imagining. I say "unfortunately," but that's where the Fringe team is concerned. For us at home, it provides a wonderfully bizarre glimpse into Walter's mind. While Peter and Olivia track down the source of the signal, believing it will lead them to Donald, Walter and Astrid remain in the lab to deal with miscellaneous hallucinations.
The running theme of Walter's trip is his fear of once more becoming the Walter of yore – the man who nearly destroyed two whole universes and regarded himself as a god. That part of him is represented by Carla, the lab assistant who died trying to eradicate some of Walter's more dangerous work. During his trip, though, she seems to be guiding him towards just what her real-life self fought to avert. She strokes his ego and whispers that the Observers would revere a man of his brilliance. She leads him to a hidden journal full of dangerous ideas, even as a hallucinated Nina Sharp tries to lead him back onto the path of goodness.
Peter and Olivia eventually find the signal's source, but there's no Donald. Instead, there are two Resistance fighters and the Junior Observer left in their care by Donald some 15 years earlier. They've since named him Michael, but he hasn't said a word in all the years they've cared for him. He only seems to perk up (by Observer standards) when reunited with Olivia, whom he remembers from the other timeline.
There is a veritable ton of other weirdness and plot developments, including hints as to where Walter's solution may ultimately lead. There are also winged fairies, a Gilliam-style animated sequence, an appearance by Gene (sort of) and other strangeness that may or may not make sense in the full recap. Stay tuned.