ARM is a science fiction novella by American author Larry Niven. Set in the Known Space Universe, it is the third of five Gil Hamilton detective stories. Published in Epic Magazine 1975. Republished in The Long Arm of Gil Hamilton (1976) and Flatlander (1996).
Hamilton is called to the scene of a murder. The victim is Dr. Raymond Sinclair, a brilliant scientist who has invented a mysterious device that creates a bubble of accelerated time. The murder scene is a locked apartment at the top of a high-rise, where the prime suspect is a beautiful young woman whom Gil refuses to believe is the killer.
One of the themes running throughout the story, and in fact a vital element in the solution of the mystery, is the loss of an arm. Gil himself lost an arm and had a new one grafted on, using parts from an organ bank which is supplied by the bodies of criminals and “corpsicles”, people who underwent cryogenic suspension. At the scene of the crime, a beautiful young woman is discovered unconscious in an “autodoc” (a device for fixing minor injuries or preserving life until help arrives) recovering from the loss of one of her arms. Another character in the story also lost an arm previously, but regards grafts as immoral and wears an advanced prosthetic arm instead. The “accelerated time bubble” has the effect of amputating the arm of anyone who reaches into it, since the arm’s metabolism speeds up to the point where the rest of the body cannot supply it with blood.