A Goodreads user asked:
what happens to po and katsa in bitterblue?
This answer contains spoilers… (view spoiler)[Their relationship takes a turn for the worse. Po wants to tell everyone about his grace, but Katsa warns him that it would be dangerous. With blunt disregard, Po tell Giddon about his grace. Katsa is very angry at Po, and sets of to explore a secret tunnel in the middle of the night, wearing only bedsheets, leaving Po crushed and alone for months. (hide spoiler)]