Chapter 154 might be a crucial turning point. It could focus on resolving a long-standing conflict or introduce new elements that change the direction of the story. Maybe it deepens our understanding of a key character's motivations.
Terrified means to describe extreme panic and fear, causing people to feel extremely shocked and terrified. Calmness meant that one's thoughts or spirit were calm without uneasiness or suppressed feelings. One had suppressed or re-restrained one's feelings and calmed down.