Basket starts in the chest room by the library with a quick update before heading down to an abandoned mineshaft under the base. The goal is simple: "I want to find melon seeds."
Books first
Since the last episode Basket has been killing "a bunch of guys" in junk armor, since they have thorns and the good armor would wear down. That and some enchanting have filled a large chest with enchanted books: Fire Aspect, Silk Touch, Power IV, Unbreaking III, Looting and more. The Silk Touch book is "a fairly rare book," maybe for shears "if I wanted web," or maybe for another diamond pickaxe.
The useful ones go on the weapons. By the next tooltip the sword Sharpie has Sharpness V, Knockback II, Fire Aspect I, Unbreaking III and Looting III, and the bow Boomstick reads Power V, Infinity I and Unbreaking III. Basket remembers it as "Power 4," but the tooltip says V.
A spawner right away
Basket found the edge of this mineshaft while caving a few episodes ago and doesn't know how big it is. Along with the melons, Basket wants a lot of rail, which goes faster with the better pickaxe. Buckets of milk come along in case of "poisonous spiders."
Almost at once Basket breaks into a mossy room with a spawner and two zombies. "Oh, look at this! I wonder how close this is to the other one." As Sharpie hits them, they catch fire.
The chest holds cocoa beans and an enchanted book with Fire Aspect II. "Pretty cool find already." Basket guesses it is "probably too far away from the other one to really hook them up."
Dead ends
Then comes a long stretch of tunnels, cobwebs, water currents and spots Basket dug out while caving earlier. "It's easier to get lost in these things. ... Like I'm lost right now." The mobs don't show up either: "This is the most mob free mineshaft I've ever seen." Along the way Basket explains the plan. Melons mean healing potions, and a skeleton spawner would mean a steady supply of bones.
Melon seeds
About halfway in, a minecart with a chest sits on a rail at the end of a tunnel.
"Yes, melon seeds, exactly what we want." The cart also holds pumpkin seeds, bread and lapis. Basket takes the melon seeds, leaves the rest and breaks the cart "so that I don't run across it again later and get all excited." "Great, mission accomplished already."
Creepers and spiders
Basket keeps going to collect more rail. A creeper gets right up close and explodes, and in the scramble the sword isn't where it should be. "Oh no! That's bad. Where's my sword?" It had been swapped with the rail in the hotbar. "That was certainly exciting." Basket thinks this part of the mineshaft cuts into caves, which is why the monsters are here.
Next is a spider spawner. Basket already has one, so this one doesn't matter much. Spiders keep coming, and Basket drinks milk between fights, since "the milk cures the poison effect." Torches go up around the spawner, and the search for a chest comes up empty. "Usually these things don't have chests."
Pillaring out
Basket thinks the mineshaft sits "basically below my base," maybe more toward the desert. With the melons and "quite a bit of rail," it's time to find the surface. Next episode is the library. After that, maybe a Nether portal, and then a stronghold "to get some brewing going," so zombies can get a splash potion instead of a long fight.
One more minecart chest turns up first. "Oh, sweet! I'm glad I didn't tunnel out yet." Basket calls it "some more melon seeds and some junk." Then, unable to find the way back, Basket decides "we'll just pillar out right here." The episode ends with Basket alive, digging up through the dirt.