Englishwoman Evelyn Wingate, Valerie French; American reporter Jonathan Clark, Gene Barry; Chinese peasant Su Tan, Marie Tsien; German physicist Klaus Bechner, George Voskovec; and Soviet soldier Ivan Godofsky, Azemat Janti, are randomly transported to an alien spacecraft in Earth orbit. There they meet a humanoid who calls himself only “The Alien,” a serene and enigmatic ambassador who explains that he represents a world orbiting a sun that is about to go nova. With a stark moral constraint against killing intelligent life, The Alien presents each of the five with a set of three capsules housed in clear, round cases. Each trio is capable of obliterating all human life within a 3,000-mile diameter, and the alien’s hope is that humanity will unleash these capsules on itself within 27 days, leaving Earth free for the aliens to inhabit. The capsules can only be opened by the thought waves of the person to whom they were given, and once activated in the open, they can be used by anyone. If one or more of the five die, their capsules self-destruct and become harmless. The Alien further explains that if humanity does not destroy itself, the Aliens cannot invade and will perish, and that the capsules’ power will be nullified if misused.
Back on Earth, Eve throws her case into the English Channel and boards a flight to Los Angeles. Su Tan decides to take her own life, and her capsules self-destruct. The remaining three try to resume ordinary life, but The Alien seizes control of all Earth’s communications and publicly reveals the existence and power of the capsules. The broadcast triggers a cascade of fear and confusion: Bechner is struck by a car while crossing a street and is rushed to the hospital, while Godofsky is detained by his superiors who demand a coherent account of the mission. Arriving in Los Angeles, Eve is confronted by a now-disguised Clark who escorts her to a closed race track where they can hide from scrutiny. Godofsky is interrogated by a Soviet general, whose dissatisfaction with the vague report leads to intense, brutal questioning.
Panic spreads as the revelation spreads, and the strain shows in the lives of those involved. Bechner endures beatings and refuses to divulge the details of the Alien’s plan, while a man who resembles Clark is killed by a mob, adding to the confusion and danger. Eventually, Clark and Eve reveal their identities and are taken into government custody, while Godofsky’s testimony becomes a key clue for the authorities. Through the use of sodium pentothal, Soviet investigators uncover the Alien’s strategy and obtain access to the capsules. The Soviet announcement heightens global anxiety and prompts the remaining three to cooperate with the authorities. A dramatic test of Bechner’s capsule is conducted to gauge the Soviet threat, with a dying volunteer left on a raft near the 3,000-mile boundary, while the U.S. Navy destroyer that delivered him remains safely outside that limit. Bechner faces mounting pressure to open his case, but the admiral confiscates the capsules and reads the coordinates aloud; the subject is instantly vaporized. This display of power convinces the United States to withdraw its forces worldwide, aligning with the Soviet stance.
Aboard ship, Bechner, Clark, and Eve discuss countermeasures and reflect on the delicate balance of power. Bechner discovers a hidden mathematical code imprinted on the remaining capsules—an imprint that governs life and death. As the Soviet general prepares to deploy the capsules, Godofsky makes a move, knocking them from the general’s hands and sending them tumbling over a two-story drop. In that split second, Bechner activates the remaining capsules. The code triggers a planet-wide sonic wave from space, targeting and eradicating every “known enemy of human freedom.” The Earth is then shown a vision of unity as humanity, under the auspices of the United Nations, extends an invitation to The Alien and his race to coexist peacefully on Earth.
The closing revelation reframes the entire sequence as a test of humanity’s character. The Alien accepts the invitation, signaling a hopeful dawn for humankind. The story ends on the note of a new era, where Earth’s governance and international cooperation are poised to redefine contact with extraterrestrial life, and where a cautious but genuine peace becomes a possibility rather than a dream.
