Episode 4 of Season 3 is a stream that picks up right where Episode 3 stopped, with the BasketCase3 colony's Electrolyzer rooms half piped. Most of it goes into Gas Filters that should split the hydrogen from the oxygen, and into finding out why the pipes keep reading blocked. On the way, the colony opens a locked room with a strange brain machine inside. By the end, sixteen duplicants are alive, oxygen is flowing into the base, and a new bedroom is marked out.
Sorting the gases
The plan from the start: "I was gonna move hydrogen over first and then I'll deal with the oxygen in a little bit." The gas from the Electrolyzer rooms goes up into a pipe, a Gas Filter set to Hydrogen pulls the hydrogen off for power, a second filter pulls out the oxygen, and "whatever is left, which won't really be much," gets dumped. Oxygen pipes then run down to the rooms that need air most.
A new duplicant is ready early on. The pick is Max, a Level 7 Runner with some Medicine. The commentary is pleased with the run so far: "nobody's dead."
The pumps soon stop with "pipe is blocked," and the readouts are confusing: "it's telling me just what was in the air, it wasn't actually telling me what was" in the pipes.
The brain behind the door
The colony has run out of algae, and the hunt for more turns up a door that "requires a sample to unlock." Inside is a desk with "a barely functioning computer" and a Neural Vacillator, "a massive synthetic brain suspended in saline solution," with a chair for one. Reading its log, the commentary's verdict is "That's weird."
Mae is sent to sit in it. When it finishes, the game reports that Mae "acquired the Deeper Diver's Lungs trait," and the machine has "no charges left."
The blocked bridge
Back at the pipes, the blockage gets worse. Pipes are rebuilt, reversed and swapped out, and the hydrogen backs up at a Gas Bridge that reads "Not Pumping." Running the bridge through the floor instead fixes it: "I guess you can't bridge through part of this structure."
Then the hydrogen generators show "Insufficient Resources." A sixteenth duplicant is printed, and med-beds go down so the duplicants "can clean themselves up." The last jam turns out to be a filter with nowhere to send its oxygen: "if it doesn't actually have an outlet, it just doesn't function." Vents go into a room that has little air, and the gas starts moving.
A bedroom with its own air
The colony keeps running low on oxygen, enough that the duplicants "had to run into that room to be able to breathe." One oxygen line is given a single job, a new bedroom with an airlock and vents. A pipe bridge stops the water feed from cycling back on itself, and "now we'll just start producing oxygen again."
Where it ends
"Look at all this oxygen. I think we have solved that problem." By the last minutes, "Insufficient oxygen generation" is gone from the alerts. Rows of beds are laid out for the new bedroom, the old ones are marked to come down, and the water tank is about to start draining, with more filters left for "next time."