The story, told from the perspective of an older "local" man, begins as he is sitting around at a convenience store with a group of his friends during a heavy snowstorm. A young boy runs in, deathly afraid. The men recognize him as Timmy Grenadine, the son of Richie Grenadine, a man who was injured in a work accident at the local mill many years ago and was granted lifetime workmen's compensation to ward off a lawsuit. Richie's wife died prior to the accident, and the marriage produced the minor son who is now seeking refuge. Now that his son could be cared for thanks to the continous generous income, and no need to support a wife nor himself, Richie became a recluse, drinking cheap beer while watching TV, and using his son to act as errand boy for the times errands needed to be done, most of which involved buying beer.
After speaking privately with Richie's boy, the narrator, Henry, and one other local decide to take the beer to Richie personally. On their way, of the terrifying experiences the kid had told him — of how one day his father drank a "bad" can of beer and since has been slowly transforming into an inhuman blob-like abomination that detests light and craves warm beer, and soon got to the point the son needed to open the beer cans for his dad as Richie's hands mutated into tentacles, the sole time Richie used light to show the mutation and said it is not painful, but feels "kinda nice". Shocked, Timmy said he would call for a doctor, but Richie threatened that if he told anyone of the mutation he would touch Timmy and turn him into a fungus monster as well. Richie soon demanded Timmy stop using all electricity, even the light coming from the crack of the bedroom door was too sensitive, so Timmy took to going to a schoolfriend's to get his homework done. While Timmy was spying on his father saw Richie eat a dead cat, to which he felt sufficiently frightened he ran away. With no immediate family, he sought refuge at the general store as Henry, the store's owner and manager, was the person he knew best through the constant business he had done on behalf of Richie. Henry and the local men decide to get to the bottom of the matter by personally delivering the beer to Richie.
Arriving at Richie's home, a Victorian home which had once been owned by a paper baron then later sold and converted into an apartment building, the men are aghast by what they see. The floor Richie lives on has torn carpeting and a vicious odor emanating from Richie's residence. The narrator (one of the men beside Henry) wonders why this was never brought to the landlord's attention, and another man asks "Who registered a complaint?" showing that all the apartments on Richie's floor are unoccupied. Although the vacancies appear that Richie's stench ran them off, it could also imply Richie was eating far more than dead cats. Henry demands Richie show himself. Richie, in a gargly voice, demands to know what happened to his son, to which Henry replies the son is with his wife, having a meal at Henry's residence. Henry also remarks the kid is skinny as a rail, implying Richie has been neglecting. The men only get Richie to show himself when they offer him a case full of beer.
The men are horrified when Richie opens the door, and shambles out. No longer resembling anything human, Richie is more fungus than man. Worse yet, he appears to be in the process of dividing. This scares all the men, who retreat, save for Henry, who draws a pistol and open fires on the creature.
The story ends with the narrator calculating the exponential growth the creature is capable of, as they sit at the convenience store, waiting to find out who survived, Henry or the creature. The men remark that they are sitting at the door, drinking their beer, while the narrator thinks to himself "I hope it is Henry, I really do".