Lion's Den features Marta, a lesbian inmate, who forms a deep, protective, and emotionally intimate bond with protagonist Julia and her son. This relationship is depicted with dignity and serves as a vital source of support and resilience within the harsh prison setting. The film portrays Marta as a complex character, affirming the worth of her identity and her bond without resorting to stereotypes or negative framing.

The film strongly endorses alternative family structures, portraying a single mother's resilience within a supportive 'chosen family' in prison, and prioritizing these bonds over traditional biological family claims and gender roles.

The film portrays Sister Marta, a Catholic nun, as a compassionate and supportive figure who provides essential aid and moral guidance to the incarcerated women and their children. Her actions reflect a positive influence of the faith within a harsh environment.