The protagonist of the story is Scanner Martel, set apart by his marriage to a normal woman. At the start of the story he has cranched and is trying to relax at home, but is ordered to an emergency meeting of the confraternity (such a major emergency that it even over-rides the protocol permitting a cranched member to decline to attend). The leader of the Scanners, Vomact (a member of the vom Acht or Vomact family which plays a prominent role through much of Smith's Instrumentality future history), informs the meeting that one Adam Stone is about to make public a method to prevent the Pain of Space in normal people, thereby rendering Scanners obsolete. The Scanners vote to kill Stone, and only Martel in his cranched state and his friend Chang (the only Scanner who, via long practice, can appear "normal" when not cranched) can grasp the moral and practical wrongness of this decision. When they are the only two dissenters to the murder vote, Martel tries to reach Stone before the appointed assassin and warn him. In order to enter the city where Stone lives without revealing himself to be a Scanner, Martel breaks off his specially formed fingernail, used by scanners to communicate by writing on a board attached to their chests, and symbolic of the status of being a scanner.

Martel succeeds in warning Stone, who reveals that he has also developed a new surgery that will return Scanners to normal. At this point the assassin arrives, who turns out to be Martel's other best friend, Parizianski. In a high-speed battle, Martel ends up killing Parizianski before lapsing into unconsciousness from the pain of operating in high-speed while cranched. When he awakens, he finds that he is the first Scanner that Stone has restored to normality; the Instrumentality plans to appoint all of them to be spaceship pilots, allowing them to maintain their guild, and they have agreed, albeit some reluctantly. At the very end, Martel learns from his unsuspecting wife that people have been told that Parizianski died because he was so happy upon learning the truth from Stone that he forgot to self-monitor.