Knock at the Cabin features a gay couple as its protagonists, portraying their relationship with genuine affection and respect. Their queer identity is integral to their family unit but not the cause of their suffering, which stems from external apocalyptic events. The film ultimately affirms the strength and value of their love.

Andrew, Leonard, and Adriane, who were depicted as white in the source novel "The Cabin at the End of the World," are portrayed by actors of different races in the film adaptation.

The film's narrative explicitly adopts a Christian morality framework, portraying themes of divine reckoning, sacrifice, and salvation as real and necessary to prevent global catastrophe. The climax affirms the efficacy of a sacrificial act rooted in Christian motifs, aligning the narrative with the faith's core tenets.