Kiros was an Arkarian member of a group of mercenaries that boarded the USS Enterprise-D during preparations for a baryon sweep in 2369 at Arkaria Base with the intent of stealing trilithium resin. During their mission, one by one, the mercenaries were subdued by Captain Jean-Luc Picard (who they thought was the ship's barber, Mot) or (in the case of the ill fated mercenary Neil) murdered by their leader Kelsey.
Their group eventually was reduced to just her and Kelsey. It was then Picard revealed his true identity and offered himself as a hostage in place of the trilithium resin they intended to steal.
Just before her escape with Kelsey she was knocked unconscious by a small powder explosion set by Picard in Ten Forward. Almost immediately after the explosion she was killed by the baryon sweep passing through the ship. (TNG: "Starship Mine")