Several hours after receiving Brandon's death message, Carl works off his frustration in the training room by beating on wooden dummies, but his Bare Knuckles skill does not increase. Donut and Katia train separately without speaking to him, showing the lingering emotional weight of earlier events. Carl then joins Mordecai in the newly expanded crafting room, where Mordecai studies the altered crafting system and tells Carl to set up the alchemy, sapper, and engineering tables before leaving on other business.

Carl unloads his supplies and experiments at the engineering table with magical tools and scavenged gear from earlier fights. He tries reshaping a giant iron breastplate with the Goo-inator, earns his first crafting achievement, and opens a Bronze Crafter's Box that gives him basic tools and an unwanted bucket of glitter. When Carl asks about welding, Mordecai explains that the shaping tools can improvise joints but can also ruin materials or cause serious accidents. Carl also passes along Bautista's location and route plans so Mordecai can add them to the growing transit map.

After cleaning up and using his pedicure kit, Carl, Donut, Katia, and Mongo visit Limp Richard's general store. The group buys only a padded mallet after Donut haggles down the price, though Carl becomes very interested in an extremely expensive battery fabricator that converts mana potions into charged batteries. Because the machine costs far too much, the group settles for selling miscellaneous junk. Carl then notices Limp Richard's science-fiction book, learns the isolated shopkeeper is starved for reading material, and trades five Louis L'Amour westerns for five of Limp Richard's books. Carl does this partly out of sympathy and partly because he expects the mole to value future book trades even more.

The team next scouts the station's rail options instead of immediately boarding the Nightmare Express. At the platform, Carl studies the map and learns that the Nightmare Express runs a figure-eight route with only five stops, looping back to station 83 through differently colored intersections, which confirms just how confusing the Iron Tangle is. They then inspect the yellow line, where a train arrives carrying monsters. Donut kills one from the safety of the platform, and Katia relays Hekla's report that many crawlers have been exploiting this mechanic for easy experience and that monsters appear to disembark every five floors into cave systems. Carl concludes this is probably not a bug but a deliberate time-wasting trap, and he tells Katia to coordinate with Hekla so their allies can feed route data to Mordecai's map.

For about an hour, the group farms arriving yellow-line trains from the platform. They discover the two recurring enemy types are level 19 Cave Mudge Bonkers and level 20 Shock Chompers, and they safely practice attacks because the monsters cannot effectively retaliate from inside the train. However, the gains are slow, and platform kills prevent normal looting unless the creatures are dragged out. Because the rewards are poor and time on the floor is limited, Carl decides they need to board a train and fight properly instead of lingering.

When the next train arrives, the group enters the second car near the engine and immediately learns the first car is locked behind a door requiring a Yellow Line Engineer's Key. Before Carl can loot the first corpse, more Bonkers rush in from the next car, forcing the party to use the close-quarters formation they had recently practiced. Carl holds the center, Donut rides his shoulder, Mongo and Katia anchor the sides, and the train's poles create a choke point that turns the cramped car into a kill zone. Katia painfully reshapes her body for the fight, Donut coordinates Mongo, and the party quickly kills the attackers. Their success proves the formation works in the train's tight interior just as another wave charges in, setting up continued combat deeper in the yellow line.