The Soft Weapon is a science fiction short story written in 1967 by Larry Niven, set in the Known Space universe. It was the basis of the Star Trek: The Animated Series? episode, The Slaver Weapon?. The original idea for the episode later became Niven's novellette The Borderland of Sol.
The Soft Weapon was first published in If (magazine) in 1967 and has since been included in the short story collections Neutron Star (1968, together with Neutron Star 1966, At the Core 1967, Flatlander 1968, Grendel, The Handicapped and A Relic of Empire) and Playgrounds of the Mind (1991)
They stop at Beta Lyrae to sightsee where they unexpectedly discover, by deep radar, another stasis box. However, the box is a trap by Kzinti pirates. The rogue Kzinti are using a dummy stasis box to lure ships that they detect to be in possession of stasis boxes. The Kzin capture the crew and open the looted stasis box, which is revealed to be a Tnuctipun stasis box, not Thrintun. Stasis boxes (which are rare) often contain advanced technological products of immense military value. The Kzinti hope to use the contents of the box to develop weapons technology that will allow them to wage wars of conquest.
The box contains a Tnuctipun weapon which is capable of morphing into several devices, none of which are deemed useful by the Kzinti as war weapons. However, one setting, an energy absorber, causes the Kzinti restraint field to fail, allowing Jason and Nessus to escape with the weapon. They are recaptured, but not before Jason manages to discover a hidden setting. This setting is a matter-to-energy conversion beam, which is far more powerful than anything possessed by either Human or Kzinti.
The Kzinti, desperate to know how to access the hidden setting, threaten Jason's wife in attempt to get him to divulge it, but he refuses. Her life is spared when the device, which is intelligent (and loyal to its long-extinct Tnuctipun masters), begins to speak. The Kzinti converse with the weapon, believing they are getting knowledge of how to access the setting. However, the weapon, believing itself to have fallen into the possession of an enemy, tricks the Kzin into activating a self-destruct mechanism. The Kzinti are killed, the humans and Puppeteer survive, in part thanks to the restraint technology used protecting them from the blast impact.