As New York City's Unidyne Building is thrown into darkness, peace worker Charles Calvin falls from his 27th-floor window. David Stillwell descends the long stairway that leads to street level, but he soon realizes that he cannot remember people he meets, among them Shela, who apparently know him. When he returns to the building, he finds that there are no stairs and that offices he has remembered do not exist. Going to his own apartment, he meets Lester, a gunman who wants to take him to "the Major." David knocks Lester unconscious, then goes to the police, but his story is not believed because he cannot remember where or when he was born. He goes to psychiatrist Dr. Broden, who refuses to help him for fear of becoming involved with the police. Detective Ted Caselle takes on the challenge but is quickly murdered in his office. Threatened now by two gunmen, David returns to Dr. Broden, and together they deduce that he is a physiochemist and that he lost his memory when he saw his best friend, Calvin, fall to his death. Now it is recalled that David had discovered the secret of neutralizing radioactivity at its source, that he had taken his discovery to Calvin, and that then he had attempted to destroy the formula when it became apparent that Calvin, for mercenary gain, wanted to pass it on to his business associate, Major Crawford. Trying to prevent the burning of the formula, Calvin fell to his death. Now recalling everything, David returns to the Unidyne Building and comes face to face with Crawford. Intent on obtaining the formula, Crawford threatens David, but Shela comes to his rescue.
