In 1958, the "Water Drop Project" was launched for basic research on submarine theory. Once the project was launched, it became a thorn in the side of the enemy agents, and in turn they made a sabotage plan code-named "Operation Rock". Police officer Pang Hongmei received the important task of protecting the "Water Drop Project", and in the midst of the obstacles set up by U.S. and Chiang Kai-shek agents, she rescued Ji Danyang, a patriotic scientist who has returned from America, from the hands of the enemy agents, and escorted Ji Danyang to Lumen City to take part in the "Water Drop Project". The enemy agents concentrated their forces to sabotage the "Water Drop Project". Pang Hongmei fought a life-and-death battle with the enemy in Lumen City, thwarting the enemy's plots, eradicating the remnants of the enemy agents, and ultimately protecting the "Water Drop Project" to achieve the desired success. After that, Pang Hongmei and Ji Danyang, who have been through the test of life and death, also fulfill their dreams with strong revolutionary faith....