Buckeye travels west of Gallows Sound to search for a lost family member. However, during her travels, she finds out that she has most worrying heritage that links her to a person she despises. At the same time, one of her crewmembers is captured by a feared organization of slave traders and Buckeye is forced to not only save her friend but also an old enemy. If she fails, not only the Twenty-One Butterflies will suffer for it, but everyone else as well. 
Ascension part 1 is the fourth book in the Chronicles of the Twenty-One Butterflies pirate fantasy series. If you have not read Butterflies Islands, Maelstrom, or Wailers, I suggest you start there to get the most out of Ascension part 1.