The Derranged Mutant Killer Snow Goons started when Calvin attempted to summon a snowman to life. He succeeded but all too well. The snowman did come to life but it turned out to be hostile. Scared, Calvin retreated to his house. They snowman followed him but ended up on the front porch. Calvin attempted to warn his mother but she didn't believe him.
Later in the day, Hobbess joined Calvin. They built a fort made of snow and used it to hide from the snow goon. Their first strategy was to kill the snow goon by hitting it with snow balls. This didn't work and instead gave the Killer Snow Goon an idea: build copies of itself. The snow goon began by making a head and attaching the head to its own body. Moments later, Calvin and Hobbes were approached by Susie Derkins, Calvin's next door neighbor. Like Calvin's mother, Susie didn't believe him.
Meanwhile, the Snow Goon was duplicate itself by building other evil snowmen. Calvin noticed one of them walk by his fort. He realized that the original Snow Goon was building an army of other Snow Goons. Hobbes and Calvin managed to remain hidden until they came inside and went to bed.
That night, Hobbess noticed that all of the Mutant Snow Goons were asleep. He and Hobbess waited until midnight when Calvin's parents were asleep. Sneaking outside, Calvin turned on the faucet. Using a house, he managed to turn melt all of the snow goons. Afterwards, he and Hobbess were brought inside by Calvin's father before going back to bed.
The next day, Calvin attempted to explain the Snow Goons to his parents but they didn't believe him. They punished Calvin but sending him to his room. After his punishment ended, he decided to never summon another snowman again.