Episode 9
That was a pretty dumb character-centric episode. They had a few different things going on in the episode - Rayet's unhappiness, Slaine's "rescue", and the PTSD treatment. The sad thing about the writing on this show is that none of it really exists for actual character development or natural narrative progress. Instead everything feels designs to exist only to feed the audience pieces of information which were deliberately being withheld for dramatic purposes. There were any number of flashbacks they could have used to show what really happened to Humery. Instead they dragged it out and in the end it's nothing shocking or surprising.
The debt Saazbaum feels he owes Slaine's father is another example of how they withheld information to make character decisions look more random or stupid, only to reveal it in the most matter of fact way which makes the characters look even more artificial and stupid. The narrative logic is all over the place and does nothing to build characters effectively. Instead when they need something "dramatic" to happen, they just force it into the script - the final scene in the episode is exactly that. It's forced, and instead of being shocking it comes off as stupid.