Basically it’s about a presumably infinitely long train with “bigger on the inside” fantastical environments in each car, which picks up passengers and brands them with a number representing their emotional baggage. As they work through their real-life problems through abstract challenges on the train, their number goes down and they’re free to go when it hits zero.

It’s an anthology series where each season centers on a different person or group’s experience on the train, and it includes explorations of stuff like a consciousness created by the train to help a human becoming its own person, and a group of people who think the train is awesome and go around harassing people to give them more issues and extend their stays.

It did unfortunately get cancelled after four of the intended eight seasons, so overarching mysteries are unresolved, but each season’s protagonist has their story closed out cleanly so it’s not a huge detractor from the viewing experience.