ARM is a story in Known Space by Larry Niven. It is the second of five Gil Hamilton detective stories Known Space is the fictional setting of several science fiction novels and short stories written by author Larry Niven. ... Laurence van Cott Niven (born April 30, 1938) is a US science fiction author. ... Gilbert Gilgamesh Hamilton is a fictional character in the Known Space universe created by Larry Niven. ...

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. A locked room mystery is a sub-genre of detective fiction wherein a murder or other crime is apparently committed under impossible circumstances: no one could have entered or left the scene of the crime, and the death involved could not have been a suicide. ...