The story is set in the drawing room of Les Cerisiers sanatorium, which is a psychiatric home for the mentally ill, run by a doctor and psychologist, Mathilde von Zahnd. The main room, where the play is set, is connected to three other rooms, each of which is inhabited by a patient. These three men, who are all “physicists” by trade, are permitted use of the drawing room, where they are monitored and checked on by the female nurses. Herbert Georg Beutler is the first patient, and he is convinced that he is Sir Isaac Newton. The second patient is Ernst Heinrich Ernesti, who believes himself to be Albert Einstein. The third patient is Johann Wilhelm Möbius, and he believes that he is regularly visited by the biblical King Solomon. In reality, “Sir Isaac Newton” and “Albert Einstein” are spies from different sides of the cold war conflict.
Once the play begins, it is revealed to the audience that "Einstein" has just killed one of his nurses, and the police are examining the scene. The “Inspector” continuously questions Fräulein Mathilde von Zahnd and indirectly insults the “mentally ill” patients.
It is revealed through their discussion that this is the second murder of a nurse by one of the three patients in just three months. The first having been committed by "Newton", which is later revealed to be a result of the nurse’s discovery of “Newton’s” real identity.
The motives behind the two murders become clearer as the play advances into the second act, where it is revealed with startling abruptness that not even one of the three patients is actually mad; they are all only faking insanity for various reasons.
Möbius is actually an incredibly brilliant physicist whose discoveries include such fabled results as a solution to the problem of gravitation, a "Unitary Theory of Elementary Particles", and the "Principle of Universal Discovery". Fearing what humanity could do with these powerful discoveries, he feigned madness, in hopes that he might be put in a home for the mentally ill and thus be protected along with his knowledge.
However, he failed to avoid attention which he so dearly feared. "Einstein" and "Newton" are both spies, representatives of two different countries, and they have infiltrated the Les Cerisiers in order to secure Möbius' documents and, if possible, the man himself. Each spy had to murder a nurse to protect his secrets and to strengthen his simulation of madness, as well as to further conceal their identities.
In the play's climactic scene, the three men reveal their secrets, and each of the two spies attempts to convince Möbius to come with them. Möbius, however, persuades them that the secrets he has discovered are too terrible for man to know and assures them that their efforts are in vain because he recently burned all the papers that he developed during his time in the sanatorium. After much debate, the three men finally agree that they are content to protect humanity by living out the rest of their lives in captivity, while furthering and serving physics.
These noble plans are quickly changed by the play's final plot twist; Fräulein Doktor Mathilde von Zahnd enters the room and reveals to the three men that she has eavesdropped on their entire conversation. Furthermore, she admits to knowing about Möbius for years and has been secretly copying his documents. She reveals that she has been using his scientific discoveries to construct an international empire which she would later rule. She believes that King Solomon is speaking to her, and she believes that with his guidance and Möbius' discoveries, she can become the most powerful woman on earth.
The story ends with a sense of impending doom. Möbius, "Newton", and "Einstein" have been tricked and trapped. The play ends with each of the men speaking to the audience, emphasizing their plight and the plight of all humanity. In their eyes, humanity was lost and could not be helped.
