Joseph is a young Englishman serving a mandatory tour as a Defender on the country's massive coastal barrier. Disconnected from the civilian world and resentful of the older generation's environmental failures, he initially focuses on his own survival and his goal of joining the elite class. As the freezing conditions wear on him, he seeks meaning through camaraderie with his shift mates.

The Captain is the imposing, highly disciplined commander of Joseph's company. Recognizable by his facial tribal markings, he originally arrived as a climate refugee before earning citizenship through his needed skills. He demands absolute perfection from his troops, enforcing strict adherence to the rules to survive the harsh conditions.

Hifa is a practical, determined Defender serving alongside Joseph. She handles the bleak environment by focusing on tangible benefits, openly discussing her desire to participate in the government's reproduction program to secure better living conditions. Her straightforward approach to survival frequently challenges Joseph's more guarded nature.

Hughes is a slender intellectual who stands out among the hardened border guards. He practices meditative martial arts in the mornings and harbors quiet plans to study Romantic poetry at university. His ability to maintain a focus on the future provides a distinct contrast to the intense, short-term survival mentality of his peers.

James is an ambitious junior politician who visits the barrier to distribute medals and deliver patriotic speeches. Wearing shiny suits that highlight his distance from military life, he represents the insulated elite class that avoids physical service. He relies on heavy rhetoric to motivate the troops while issuing warnings about internal political dissidents.

Mary serves as the cook for Joseph's military company. With her curly hair and talkative personality, she uses her daily food rounds to socialize, providing brief moments of warmth in a deeply regimented environment. She maintains a personal goal of eventually saving enough money to open her own restaurant inland.

Sarge is a heavily built, experienced border guard serving his second tour of duty. He takes immediate charge of the new recruits, ensuring they understand the lethal stakes of their assignment. He closely emulates his commanding officer's rigid leadership style, enforcing discipline through intimidation and strict oversight.

This collective group represents the parents of the current young adult generation, including Joseph's deeply apologetic mother and Hifa's self-involved mother. Exempt from border duty due to their age, they live comfortably inland while relying on old movies and nostalgia to ignore the deteriorating global climate. Their interactions with their children are defined by awkward apologies, avoidant behavior, and heavy generational resentment.

Kellan leads an off-grid community composed of lashed-together rafts hidden from regular maritime traffic. He maintains order through democratic consensus rather than strict military hierarchy. His practical knowledge of ocean survival and his willingness to listen to his people earn him deep loyalty from the settlement's residents.

Mara is a highly capable survivor who helps manage the daily logistics of an isolated ocean community. She specializes in trapping coastal birds, using her technical skills to secure vital protein for her group. Her practical contributions keep the settlement functioning during periods of severe weather.

The Hermit is an emaciated, deeply traumatized man living alone on an abandoned offshore energy rig. He has spent so much time in isolation that he no longer speaks, instead communicating his history by arranging scraps of paper in a box. He survives by carefully rationing the installation's large supply of food and fossil fuels.