The Aliens of Valtrit — John G. Bluck

After UK spy agency employee Gina Perelli peers through an espionage camera altered by an electrical surge, she and her MI7 boss see a dozen men executed by ray guns a world away. Gina and her partner, London policeman Colin Green, go on a quest to capture a ray gun, the most important arms development since nuclear weapons. With new extraterrestrial allies, Gina and Colin follow a trail to a planet called Valtrit.