On Secret Service (also known as Spy 77) is a 1933 British spy thriller, a remake of a German film “Spione am werk”, starring Greta Nissen as an Italian spy and Karl Ludwig Diehl as an Austrian officer, focusing on their tragic romance amidst World War I espionage, where she tries to save him from incriminating evidence planted by her superiors, leading to her accidental death as he tries to fly across enemy lines with vital information.