Gene Barry as Jonathan Clark
Valerie French as Evelyn "Eve" Wingate
George Voskovec as Professor Klaus Bechner
Azemat Janti as Ivan Godofsky
Arnold Moss as The Alien
Stefan Schnabel as The Soviet General
Paul Frees as Ward Mason, Newscaster (uncredited)
Marie Tsien as Su Tan (uncredited)
The 27th Day is a 1957 American science fiction film from Columbia Pictures, produced by Helen Ainsworth, directed by William Asher, and starring Gene Barry, Valerie French, George Voskovec, and Arnold Moss. The screenplay is by John Mantley, based on his original novel.
Five people, Englishwoman Evelyn Wingate, American reporter Jonathan Clark, Chinese peasant Su Tan, German physicist Klaus Bechner, and Soviet soldier Ivan Godofsky, are randomly transported to an alien spacecraft in Earth orbit.
There, they are met by a humanoid referring to himself only as "The Alien" (Arnold Moss), who explains that he is the representative of a world orbiting a sun about to go Nova. Needing a new world to inhabit within the next 35 days, yet prohibited by their moral code from killing intelligent life, The Alien provides each of the five with sets of three capsules in a clear, round, hand-held case.
Each capsule is capable of destroying all human life within a 3,000-mile diameter, with the expectation that humanity will use all the capsules, obliterating itself, leaving the Earth free for alien colonization. The capsules' clear containers can only be opened by the thought waves of the person to whom they were given. Once out in the open, the capsules inside can then be used by anyone, but only during the next 27 days, after which they become inert.
Returned to Earth, Eve throws her capsules into the English Channel and then books a flight to Los Angeles. Su Tan chooses to commit suicide, causing her capsules to self-destruct. The others go about their daily tasks undisturbed until the next day, when The Alien commandeers all electronic communications and reveals to the world the existence and power of the capsules. Overhearing the broadcast while on a trip to the U. S., Bechner is hit by a car while crossing the street and is taken to the hospital, while Pvt. Godofsky is detained by his superiors. Arriving in Los Angeles, Eve is met by a now-disguised Clark, who takes her to a closed race track where they can hide, undetected. Godofsky is interviewed by a Soviet general who, dissatisfied with his vague story, orders him subjected to intense interrogation.
Panic over the Alien's crisis grows in the days that follow. Repeated beatings leave Godofsky in shock, while a recovering Bechner refuses to reveal the details of The Alien's plan. After two Communist agents nearly succeed in assassinating Bechner, and an innocent man who looked like Clark is killed by a mob, Clark and Eve reveal themselves and are taken into government custody. Through the application of sodium pentothal to Godofsky, the Soviets discover The Alien's plan and gain access to his capsules. Their resulting announcement fuels global anxiety, prompting the other three to cooperate with U. S. authorities. Confronted with an ultimatum for all U. S. military forces to withdraw throughout the world, the government tests one of Bechner's capsules to verify the Soviet threat: a dying volunteer is left on a raft far out in the ocean. After opening a capsule, he reads his exact coordinates out loud and is instantaneously vaporized. The U. S. begins withdrawing its forces.
On board a U. S. destroyer being used as a deterrent against the Soviet capsules being used against America, Bechner, Clark, and Eve discuss their concerns that the Soviets will use them at the last minute, avoiding retaliation. Determined to find another way, Bechner studies the remaining capsules and discovers an imprinted mathematical code on them. As the Soviet general prepares to use the capsules from a balcony, Godofsky rushes him, and the capsules fall to the ground two stories below. At the very same moment, Bechner simultaneously launches his remaining capsules and the ones from Clark's container. He has deciphered the hidden code and discovered that the capsules can be programmed. The world is then blanketed with a high-pitched sonic wave that kills every "known enemy of human freedom".
In the aftermath, at an undisclosed later time, a now united humanity invites the aliens to coexist peacefully, sharing the Earth. It turns out, however, to have all been a test of mankind's character. The Alien's sun is quite stable. He in turn invites the people of Earth to join the Galactic Federation, having now passed its crucial test.