Chapter 7 -> The team decides to try and go out and do some actual hero work and try and make themselves more useful, feeling like they were being limited to just waiting around and going after gems. They have a few successful runs, but eventually, they slip up and get cocky, Brayden ending up losing his life. Olivia, heartbroken and angry, finally let the darkness take over. We also see Samantha and Ian getting closer [End of Part 1] (maybe also here ian and allen discover they are brothers)
When Brayden dies Olivia looses control and kills everyone involved, the team unable to stop/calm her before it's too late