A medical ship, tasked with routine health inspections, arrives at a neglected planet, Tallien Three, only to find itself embroiled in a crisis. The crew, led by a medical officer named Calhoun and his companion Murgatroyd, a small alien creature, receives a warning about a dangerous situation on the planet. Upon landing, they discover that a mysterious epidemic has turned a significant portion of the population into "paras," individuals who exhibit violent and irrational behavior, driven by a grotesque craving for scavenger creatures. As Calhoun navigates the chaotic environment, he learns that the paras are not merely sick but have become organized in their madness, posing a threat to the remaining "normals." The planetary government is in disarray, with the Minister for Health and other officials struggling to maintain control. Calhoun encounters conflicting messages from various factions, including a desperate plea for help and a warning to avoid the paras at all costs. The situation escalates when Calhoun is attacked by a para, leading to a confrontation that reveals the depth of the crisis. The Minister explains that the paras are driven by a condition that makes them crave the very scavengers that humans find repulsive. Calhoun suspects that the epidemic is not a traditional disease but rather a result of some external influence, possibly linked to the planet's native ecology. As tensions rise, Calhoun realizes that the paras are not just victims of a disease but are being manipulated by a powerful figure, Dr. Lett, who has taken control of the government. Lett's vaccine, which he claims can cure the paras, is revealed to be a means of maintaining his power over the population. Calhoun deduces that the epidemic is tied to a specific organic compound that has proliferated due to the absence of natural checks in the ecosystem. In a desperate bid to save the planet, Calhoun devises a plan to introduce wood smoke into the atmosphere, a substance that will counteract the effects of the compound causing the paras' condition. He ignites a fire in the city, creating a thick smoke that envelops the area, effectively neutralizing the paras and restoring sanity to the population. With the crisis averted, Calhoun reflects on the nature of the epidemic and the societal implications of the paras' transformation. He and Murgatroyd depart the planet, leaving behind a world that has narrowly escaped a descent into chaos, pondering the future of Tallien Three and the lingering effects of the ordeal.
By Murray Leinster · First published 1950 · Genre: Science Fiction, Dystopian, Thriller · 4 chapters