Day the World Ended

Geologist specializing in uranium mining; pragmatic, calm under pressure, and a natural problem-solver who helps keep the group alive. He forms an alliance with Louise and acts as a counterbalance to Tony's scheming. His cautious, evidence-led approach contrasts with the threats outside and inside the shelter.

Daughter of Jim, engaged and emotionally resilient. She keeps hope alive in the canyon, appeals to her father's humanity, and forms a bond with Rick. Her kidnapping by the mutated creature and subsequent safe return highlight her role as a moral center for the group.

Former U.S. Navy Commander who stockpiles supplies and shelters his daughter. He is slowly dying from radiation but remains the moral anchor, revealing that rain will cleanse the fallout and allow a wider world to reemerge. He dies after delivering crucial information and sacrificing himself.

A small-time hood whose charm hides a dangerous willingness to remove rivals. He manipulates the group to win Louise's affection, murders Ruby, and attempts an ambush on Rick. His scheming ends when Jim shoots him.

Tony's moll; she confronts him about Louise's interest and is killed in the ensuing violence.

An atomic-mutated monster that stalks the canyon, preying on those contaminated by fallout. It is ultimately destroyed by the rain.

A survivor who bears the visible and unseen effects of radiation, representing the ever-present danger inside the canyon.

Louise's fiancé from a framed photograph, remembered by Louise during her confinement in the canyon.

Voiceover narrator credited in some versions, providing context for the post-apocalyptic setting.