The Aliens of Valtrit

"The Aliens of Valtrit" begins with a short introduction to the planet Valtrit and then switches to London in 2061.
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, must 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.
Because her father was murdered when she was 14, Gina suffers from Post-Traumatic Stress Disorder. She struggles to assert herself in MI7 and during combat.
She and Colin seek to destroy a private Valtritian bankers’ army intent on conquering Earth for extraterrestrial bank president, Thomas Savadge. Colin, an older man who believes women are ill-suited for the spy business, increasingly values Gina, as the pair faces dire predicaments.