This film was shot by Beijing Film Studio 1977. It is about the desperate struggle between the enemy and us around the stolen secrets of the "1 10" civil air defense project. Facing the cunning and cruel enemy, it embodies the brilliant image of our public security personnel's wit and courage. The whole story is reasonable, compact, thrilling and suspenseful. Although it has some limitations in conception because it is branded with that era, it is still a masterpiece in the anti-feature film. In the movie, many scenes that looked terrible at that time were shot, such as the scene where the inspector who broke into the enemy went to the columbarium to get the goods and met the enemy spy in the gloomy cathedral. The most unforgettable scene for me is the eyes of a female spy disguised as an old woman selling popsicles on a rainy night, which is unforgettable with the unique horror music of Chinese style. The Black Triangle broke through the shackles of movies of that era, and the good guys and bad guys no longer saw through it at a glance. For example, agents such as Huang and Owl didn't realize it until the second half. The language used by spies in prison is more elegant and tasteful than ever before. "My path is tortuous, through a sheltered valley, branches and flowers, to a retreat of Buddhism", a famous Tang poem, is actually a signal used by two spies. In the history of China's movies for a hundred years, the black triangle has always been the mainstream type of China's movies. At that time, the sensational effect caused by this film was all the rage, and at the same time, such a drama has been deeply remembered by the audience. The Black Triangle is no stranger to China audiences born before 1970s, but for young audiences who have never experienced that period, the history of Catching a Spy may make them feel fresh and curious.