There is a secret snake breeding base on the mountain in the suburbs of Haixi City. In order to pursue high production of snake skin, the boss feeds high-hormone feed wantonly, and the snakes gradually mutate... One day, an important customer came to inspect, and the ferocious group of snakes escaped from the cage and began to attack the humans in the snake breeding base frantically. The people in the base could not withstand the offensive of the snakes and all died tragically. However, the snakes were not satisfied. They crawled to a model flight attendant girls' school not far from the snake breeding base... The school is preparing for the "2021 Graduation Ceremony". Students who do not know that they are about to face danger are still participating in the school's professional skills competition. The snakes secretly poured into various places in the school, dormitories, bathhouses, corridors, simulated cabins... Several girls were bitten by the group of snakes, and the screams alarmed the entire dormitory building, and the girls fled in all directions. Security guard Liu Chao rescued Li Mengna, a flight attendant student trapped by the snakes. The two wanted to notify all teachers and students in the school to evacuate urgently, but were stopped by the principal. The principal did not believe that there was really a mutated snake group and insisted on continuing to prepare for the graduation ceremony. At this moment, in full view of everyone, the giant black snake swallowed the principal in one gulp. Finally, the human-snake survival escape officially kicked off...