In the Security Council chamber of the United Nations, council representatives debate the arrival of an alien visitor. The USSR is deeply suspicious while the U.S. advocates trust. The emissary interrupts them by teleporting in. He explains that his race sped up evolution on thousands of planets two million years ago and have kept watch over the developing races since. However, Earth has not progressed as fast as they hoped. Humans have "a small talent for war." The aliens find Earth's bickering over borders and Cold War stalemate disappointing, far short of the "better things" they bred them for. They plan to terminate the experiment on this planet. Within a day, their armada will arrive and exterminate all life on Earth. When the Soviet ambassador demands proof that they can do it, the emissary says cryptically, "keep watching the skies."
Fraser, the American ambassador, pleads the case for humanity, but is told the decision was reached after centuries of observation and debate. Fraser appeals for one last chance for Earth to prove its worthiness. The emissary agrees to wait 24 hours, and then departs. The Soviets are still skeptical, but proof comes immediately when the Royal Observatory calls and informs the council that Halley's Comet has disappeared. Convinced, the council works frantically to create a new disarmament accord.
Twenty-four hours later, the emissary's spherical spaceship arrives directly in front the UN. The treaty is just finished and has been ratified by the General Assembly. The council members are elated that world peace has finally been achieved. Fraser proudly hands over the thick disarmament treaty. The emissary leafs through it then begins to laugh heartily. They had misunderstood him. The aliens were breeding warrior races and humanity never had the savage killer instinct they had hoped for, as proven by the document. But he leaves with a laugh, having found humans quite amusing with their limited comprehension. A fleet of spherical ships descends on the city as the sky goes completely black.