This is now totally uncharted territory for me, since this is the first episode that wasn't part of the Extended Adventure. A lot of this one is Dorothy, Toto, and the Scarecrow trying to figure out what's going on, and why Scarecrow can't remember anything. Glinda eventually shows up, but it turns out to be a holographic recording on a loop. There's no sign of the real her anywhere. Dorothy eventually finds the Great Book of Records (which looks really cool here, and is only the latest volume), but the relevant page is ripped out. Examining the next page, however, shows what happened. But Dorothy also trips an alarm and causes the castle to fill with oblivion water. Ah, but Dorothy appears to have a new ally in the flying monkey that brought her into the castle, as he can talk and communicate with the other monkeys. They use the monkeys to contact West and get instructions on how to fly the castle. It isn't easy, but West eventually helps Dorothy control things and land the castle in Betsy Bobbin Park (!). So now our gang, with new member the Scarecrow, have a new mission: Find Glinda!
Lots of neat little Oz Easter eggs to look out for, like Ugu Shoes and Button-Bright Toothpaste. I also noticed in the credits that Michael Patrick Hearn, noted Baum scholar and author of The Annotated Wizard of Oz, is a consultant on the show, so it is definitely in good hands.
And if you're interested in other reviews of the show (warning, they've binged the whole thing, and so there may be a few mild spoilers for stuff I haven't talked about yet), here's one from Toonzone (he seems to like West as much as I do), and here's one from Jay Davis at the Royal Blof of Oz.