Episode 15 opens on a minecart ride down a long stone tunnel, under the INVERSION logo and a title card reading "Episode 15, Subterranean Railway, Part 1." "Hey everybody, Basket here," the narration begins. The plan with Scoti_Garbidis is to collect quartz "to pretty up this rail tunnel that we have going in between our two bases." The tunnel is already dug, and it carries on to a cattle farm "underneath Wither Island" that viewers have not seen yet. That means a lot of quartz and a lot of glowstone, so the two head for the Nether with fire resistance potions packed.
A quartz ring every five blocks
Back at Basketopia, the narration shows the design at the tunnel mouth in the dome wall: "It's a quartz ring, with five blocks in between, and then we have glowstone lamps up top." The entrance is framed in pale quartz, with a lamp set in the ceiling just inside.
The cart launcher
The station has a launcher, which the narration says is a design from another YouTuber's Nether hub. A hopper catches an arriving cart and drops it into a dispenser. Press the button and the cart comes back out; hop in, and a piston pushes a block up and sends the cart off. The first try goes wrong ("if you have lag then that doesn't really work, I messed it up"), and the second works: "That time there wasn't any lag."
Lost in the Nether
Through the portal, the narration points out a change to the Nether tunnel. It sits lower now, on a slab with a gap underneath, "so that way we can sprint away faster."
Out on the netherrack, Scoti_Garbidis turns up in yellow and pale purple armor, and the first few minutes are mostly about finding each other. "I'm already lost," a voice says. A little later: "I forgot about falling." Basket drinks a fire resistance potion and gets to work.
Quartz duty
The rule is fortune on the quartz and silk touch on the glowstone, because "it'll make the lamps cheaper in the end." The quartz piles up fast. "I got 57 quartz already," a voice says early on, and another adds, "I am loving servers that were made after quartz was added." It goes into blocks to save space, since "most of this stuff is gonna be all for the tunnel."
TheSportsfreak joins the game and types "heyas". Basket answers "Heyas!" and Scoti_Garbidis types "wassup sports!" before TheSportsfreak heads off to "work on an anima[tion]" and leaves.
On voice there is a story about a zombie pigman named "The King of Pig Island." It was slapped, and because the name tag keeps it from despawning, it has stayed angry ever since. "He is a grudge-holding pigman," a voice says. It now sits in a cage in a cathedral. Someone also has "all the supplies I need for my shifting floors."
Basket took the prank up again later on another server, in GopherCraft SMP Season 1 Episode 13.
Fortress chests
Later the two cross into a Nether fortress, with Scoti_Garbidis's nameplate showing in the dark corridors. The chests get opened to a count of "one, two, three." The first holds two diamonds, iron ingots and a flint and steel. Another has a gold ingot. A third has saddles and nether wart. "I'll take the diamond," a voice says. "And I'm taking the saddles." The netherrack stays behind.
Deeper in, Basket swings a diamond sword at a blaze, and a wither skeleton stands further down a corridor.
To be continued
Back out on open netherrack, the work gets divided: "you pillar up, get all the glowstone and the stuff on the ceiling," and "I'll get the stuff on the ground down here." The episode ends with Basket still mining among the small fires, and "To be continued..." comes up before the end card. Nothing plays after it.