Chapter 6 is blatantly a breather chapter, and unlike 64, it actually leaned into it more than just aesthetically.
Day 1 introduces the peril of the chapter- that being Beldam's suspicious threat- and runs through the motions of a whodunnit mystery. It introduces red herrings for you to dismiss, while still keeping to the theme of things that might actually be legitimate solutions to the initial threat (...although the Goldbobbingtons are pushing it). These sequences are entirely narrative focused, requiring the player to run along the length of the train to find and retrieve solutions. While this is an effective way to eliminate everybody necessary for the mystery, this may be quietly one of the more frustrating legs of backtracking in the game- especially since you have to dismount Yoshi in order to switch carriages. Without enemies to trip you up, it remains a quiet instance. There's a few frustrating Flags for repeat players, but otherwise this is the game establishing yeah, it's a better writer than designer.
Day 2 has the answer to the mystery, and follows up with the chapter's only dungeon. I kinda feel like removing the Shadow Sirens as a boss here ruins the buildup, though. Yeah, I can see them not wanting to throw Doopliss at us here, but Beldam and Marilyn alone could surely suffice. They wouldn't be as scary as they were in a trio, but I'm not really asking them to be scary- I'm asking them to follow up the Doopliss reveal by actually attempting to hinder us through more than just the Smorgs. Marilyn could guard the Ultra Boots while Beldam has a (comically lacklustre) boss in front of the switch, before she throws the Smorgs at us while we're not looking. With the Shadow Sirens disappearing from Riverside Station entirely, their absence is really felt in the emptiness of the station. Perhaps that's to let down our guards.
Day 3 is the climactic battle with Smorg. Yes, this game was contractually obligated to have a boss fight on top of the train, and yes, the Shadow Sirens could never have been dramatic enough to sub in like Magnus von Grapple can, so I am on board with the idea of Smorg. Frankly, I'm not even entirely sure explaining what his deal is can be much of an improvement. It would bog down the pacing and there's only so much "hive mind tentacle monster" lore you can make before I start questioning you for other reasons. The only lore they needed was "Beldam is the reason the Smorgs are on board the train".
At Poshley Heights itself, we see Pennington reveal himself to be not a detective- a reveal that was very apparent from hearing him talk. The joke was actually kind of funny, in a very dark "watch him talk himself into a situation he isn't smart enough to be in" kind of way, but they do kinda make him come off as if the characters are legitimately buying his detective work rather than merely humouring him, which is only sorta funny a few times and quickly turns into terrifying following the in-character logic. Mario figuring out Zip Toad feels more like it's all on the player to follow the whodunnit clues than anybody in-universe solving the case through sound logic and reasoning. "Discoloured nose hair".
Mechanically, Chapter 6 is a bunch of Flags to hit on the train, a dungeon that combines mildly frustrating platforming with far less frustrating enemies (although considering Parabuzzies and Poison Pokeys, perhaps less than intended), a boss fight that's easy to deal with and can kill you fast if you're not ready for it- a neat match for a boss that doesn't have any endurance elements before facing it- and then a short town with a puzzle that is longer for travel time than it is difficulty. Overall, you do kinda wish Ultra Boots let you walk faster as well as jump higher, but this wasn't as awful as "plot-heavy chapter in a game that has backtracking issues" would have you suggest. Besides, we don't even need to turn this star into the Door to know where number 7 is.
