Lady Blackbird is, in fact, Chapter one of Tales from the Wild Blue Yonder, three pre-built one-shot adventure modules where you play as pre-made characters, in medias res, with a carefully constructed scenario for you to play through in an attempt to fulfill your character’s goals.
It’s not as locked-down as that makes it sound. For all the pre-building these characters have gone through, there is a lot of flexibility in how the characters are played and how their backstories are revealed. You spend dice to do certain actions, and you can regain those dice by inventing and revealing bits of your backstory to other characters. You get bonus dice or XP whenever you do something that connects with your characters motivations, but its up to you how they connect. You can also buy off certain motivations and replace them with others if — in narrative — your character changes their mind.