"Millicent Barnes, age twenty-four, young woman waiting for a bus on a rainy November night. Not a very imaginative type is Miss Barnes, not given to undue anxiety or fears, or for that matter even the most temporal flights of fancy. Like most young career women, she has a generic classification as a, quote, girl with a head on her shoulders, end of quote. All of which is mentioned now because in just a moment the head on Miss Barnes's shoulders will be put to a test. Circumstances will assault her sense of reality and a chain of nightmares will put her sanity on a block. Millicent Barnes, who in one minute will wonder if she's going mad."
Millicent Barnes is confused by the actions of various employees at the bus station. The ticket taker tells her that she has repeatedly asked when the bus is going to arrive, and that her suitcase has already been checked. The washroom attendant claims she was there a few seconds earlier. Yet she hasn't done any of these things. While in the washroom, she sees herself sitting on a bench out in the bus station. She runs out, but the room is empty. Paul Grinstead, a businessman, becomes concerned for Millicent. They go to board the bus, but Millicent runs back in after seeing her other self already on the bus. Paul stays to comfort Millicent, who now says she knows what is happenning: a mirror image of herself from another world has entered this world, and must take her place to survive. Paul, certain she's mentally ill, calls the police. After the police take Millicent away, Paul chases a man who he believes has stolen his case. As the man turns around, Paul realizes that the man is a duplicate of himself."Obscure metaphysical explanation to cover a phenomenon, reasons dredged out of the shadows to explain away that which cannot be explained. Call it parallel planes or just insanity. Whatever it is, you find it in the Twilight Zone."