Episode 1 of Season 3 is a stream, and it starts a brand new colony. There have been game updates since the last time Oxygen Not Included was played here, so the commentary reads the update notes and decides to "do a new one, we're starting over." Three duplicants land, the oxygen runs short almost at once, and the rest of the stream builds up air, food, water and power. The big project is a water tank. When the stream ends, six duplicants are alive and the tank is almost ready to fill.
A new colony
The main menu shows the notes for the Oil Upgrade. The commentary reads out new oil biomes and geysers, rechargeable exo suits, room systems and a revamped research tree. Then come the starting duplicants: Ren, a runner, Joshua, a body builder, and a chef who becomes the colony's only cook. The colony is named BasketCase3. "Let's not let our guys die."
The first jobs are digging out a floor, laying tiles and putting down storage bins. Power comes from a Manual Generator wired to batteries. Oxygen is already a problem ("I'm already having O2 problems"), so the duplicants dig algae for an Algae Deoxydizer, which turns algae into oxygen. A Microbe Musher makes Mush Bars, an outhouse goes in because "they do require toilets," and cots follow. A pitcher pump, a bottle emptier and a wash basin come next, after a hint about germs.
Research and a fourth duplicant
A new duplicant can be printed, and the colony takes a scientist. A research station goes up on a new floor, and the research tree comes out. Plumbing comes first, then Air Systems, whose Carbon Skimmer "filters carbon dioxide from the air." The commentary finds an area of the base with too much carbon dioxide, and that the oxygen machine is idle there because the air pressure is too high. Better research needs a supercomputer, so one gets built and powered.
Stress starts to show, so a massage table goes in. Ren runs in the generator so much that, per the commentary, Ren "is getting better and better at running." A small critter that "makes coal" turns up, and the commentary wants to keep it alive this time.
The big water tank
"What I like to do is try to build in like a big water tank." Walls and ladders mark out a huge room, and the duplicants dig it out one layer at a time. Polluted dirt gets its own storage, away from the main rooms.
A fifth duplicant, a technician, joins. The Carbon Skimmer goes in next, and it needs water piped in and somewhere for the dirty water to go. Liquid pipes run through the rock, and a liquid pump goes into a pool of water. Power is cabled down to it as well. "Pipe is blocked" comes up, and the pump gets switched off so the tank can be finished first.
Power runs short, so a second Manual Generator goes up. An Algae Terrarium is built to take in carbon dioxide and give off a little oxygen. A sixth duplicant is printed: Mae, a physician.
Cold, a critter and full storage
A duplicant gets hypothermia in the cold, wet part of the dig. A critter turns out to be walled inside the tank area. Breaking the wall to let it out comes up, but the next report is "He drowned."
"We now have a planting area," the commentary says, and compost too. "Food is decaying," and the game asks for medical beds, so one is built. Then the sweeping stalls, because the storage is full. The storage filters get changed and the settings copied across, and sweeping goes to top priority.
Where it ends
The tank is cleared but still empty. "We almost have the water thing up and running. Not quite." The game is saved, and the stream ends with the pause menu open.