 Dr Miles Bennel returns his small town practice to find several of his patients suffering the paranoid delusion that their friends or relatives are impostors. He is initially sceptical, especially when the alleged dopplegangers are able to answer detailed questions about their victim s life, but he is eventually persuaded that something odd has happened, and determines to find out what. This film can be seen as a paranoid 1950s warning against those Damn Commies, or conversely as a metaphor for the tyranny of McCarthy-ism (or the totalitarian system of Your Choice) and has a pro- and epilogue forced upon Siegel by the studio to "lighten the tone".