Karl and Martha, two German scientists, work together in a research laboratory. Their work focuses on poisonous snakes, studying their most dangerous specimens in order to develop bite antidotes. They want to find a universal formula to avoid many deaths and paralyses. The laboratory consists of a gigantic vivarium in which about fifty of the most formidable animals live. Their size is impressive, and it is not uncommon for them to devour each other.
For their experiments, Karl and Martha must regularly catch snakes; they do so with large restraint pliers, which forcefully hold the reptile heads away from the scientists' bodies. The animals fiercely hate Karl and Martha, their sadistic torturers.
One morning, Karl has to leave because of an emergency at the nearby zoo. So Martha works alone in the laboratory. She needs to catch one of the most aggressive snakes. She holds the pliers with dexterity but imperceptibly, deprived of Karl at her side, she feels less confident than usual. The animal, a female, feels it immediately. With its head immobilized at the end of the pliers, the beast manages to propel its body by an unnatural movement, so that it is able to grab Martha's right arm. The snake crushes with all its strength, and Martha's hand wobbles like a rag doll, no longer able to hold the pliers. The next step seems inevitable: the animal throws its head towards the tender and fragrant flesh of Martha's face, in a dazzling animal spirit.
However, the scientist still carries a huge knife in her gown pocket. She grabs it with her left hand and literally knocks out the snake. It's like stunned, but it has time to bite Martha on the thigh, just before it collapses.
Martha reacts very quickly, tightens the grip of the pliers around the neck of the animal and puts it back in the vivarium. However, the scientist is beginning to feel the effects of the bite. She knows she can't survive a long time. Calling 911 won't save her, they won't have anything to heal her. She rushes to a vial stored in the refrigerator: the antidote being developed. She knows it hasn't been tested enough, but what's the other issue?
Martha absorbs the vial and sits down. Her heart is accelerating. She believes her end is near, yet her condition is improving rapidly, perhaps too much. She feels metamorphosed and sees that the skin of her arms is cracking, already leaving space for a few scales. In about ten minutes, the scientist is transformed. She has mutated into a brown, shiny and agile snake.
Karl comes back from the zoo at this very moment. Nose to nose with the snake, Karl legitimately believes that it has escaped from the vivarium. He grabs a pair of pliers, grabs the reptile and throws it into the vivarium.
Martha's suffocating. She can already see all the snakes coming forward. They have recognized her and their hatred is prodigious. They run at her in an infamous and whistling gurgling.