Owen is a new firefighter at the station, hailing from a Boston family with a strong firefighting tradition, and he develops a supportive and emotionally significant connection with Cassie.

Diana is Cassie's mother, whose past actions strained their relationship; she is portrayed as emotionally mature and complex, encouraging Cassie to explore forgiveness and emotional healing.

Comprising Six-Pack, Case, Tiny, DeStasio, and Captain Murphy, this group initially resists Cassie's presence but gradually evolves in their perceptions, representing traditional and changing attitudes within the fire department.