Del, believing he is the last man on Earth after a catastrophic event wipes out humanity, lives a solitary existence in his hometown. Residing in the library where he once worked, he spends his days cleaning out abandoned homes and respectfully burying the deceased. However, his mundane life takes a turn when fireworks disturb his peace one night. The following day, he finds a young woman named Grace unconscious in her car due to a drunken accident. Although he is initially cold towards her, Grace’s persistent nature leads Del to reluctantly agree to a trial period where they might help each other.
During this time, Grace proves to be an unpredictable yet vibrant presence in Del’s life. As he teaches her the ropes of his grim routines, she brings a sense of companionship that Del had long forsaken. When Grace finds a dog and lavishes it with attention, its swift departure after biting Del prompts a confrontation. She reminds him of her past joy, emphasizing the stark difference between her life before and his long-standing bitterness. In a moment of sincerity, Del shows her his greenhouse and seeks to reinforce their collaboration in clearing homes.
Their bond deepens when Grace discovers a house yet to be cleared, which reveals Del's family ties, including the burial of his mother's remains. An unspoken tension builds as Grace kisses Del, hinting at her deeper feelings. However, the next morning, Del's world shifts again when he meets Patrick and Violet, Grace’s real parents, unearthing the fact that many survivors of the apocalypse have formed a community unbeknownst to him.
Disturbed by this revelation, Del chooses to isolate himself once more, but Grace seeks him out, pleading to stay with him despite her claims about her true parentage. Following a visit from Patrick, who entices Del with promises of new beginnings in California, Grace reluctantly leaves with her parents. Consumed by loneliness, Del can no longer endure the solitude of his small town and journeys to Patrick's address, searching for Grace.
In a desperate attempt to reconnect, Del sneaks into Grace's new home only to discover she has undergone significant behavior modification surgery designed to erase the trauma of her past. As they attempt to flee, Patrick intervenes, arguing that the only path forward for humanity involves forgetting past losses. Chaos ensues, leading to Grace inadvertently shooting him in a panic. Despite her modifications, Violet retains memories of her lost daughter, showcasing the complexities of their collective trauma.
As Del and Grace navigate a city teeming with unrealistically cheerful survivors—people who have chosen to live in willful ignorance of their past—they realize that they aspire to return to the solace of Del's humble town, away from the oppressive happiness that now surrounds them.
