A swarm of predatory vampire bats descends upon the American Southwest, threatening the lives of those living in the shadow of the desert. The narrative follows a small group of individuals, including a local deputy and a scientist, as they attempt to understand and contain the rapidly multiplying threat. As the creatures expand their hunting grounds, the protagonists must navigate the harsh terrain and the limitations of their own resources to survive the onslaught. The story unfolds through a tense, atmospheric lens that emphasizes the vulnerability of human settlements against a relentless, biological terror.

This novel is frequently cited as a notable entry in the 1970s and 80s creature-feature subgenre, characterized by its focus on biological horror rather than supernatural entities. The narrative relies on the mounting dread of an encroaching, natural threat to drive its momentum, reflecting the era's interest in ecological anxieties. Readers often note the author's ability to maintain a clinical, journalistic tone even while depicting gruesome encounters with the swarm. The work stands as a representative example of suspense fiction that prioritizes atmospheric tension over traditional monster tropes.