The old abandoned house on Benefit Street has long been a source of fascination for the narrator and his uncle, Dr. Elihu Whipple. Intrigued by the mysterious sickness and death that have plagued previous inhabitants of the house for over a century, the two have dedicated themselves to uncovering the truth behind its dark history. Along with the peculiar weeds in the yard and the putrid smell emanating from within, the cellar harbors an eerie discovery - whitish phosphorescent fungi and a strange, yellowish vapor.

Driven by their desire to confront the possibility of a supernatural force, the narrator and his uncle decide to spend a night in the house. Equipped with military flamethrowers and a modified Crookes tube, they prepare to face whatever may come their way. As they settle into their makeshift accommodations in the cellar, Dr. Whipple succumbs to restless sleep, punctuated by incomprehensible ramblings in French and disturbing visions of grotesque scenes within the shifting walls of the house.

It is when the narrator himself falls asleep that the true horror unfolds. Awoken by a blood-curdling scream, he is confronted by a revolting yellowish glow emerging from the floor. The ghastly light, seemingly endowed with multiple eyes, vanishes through the chimney, leaving the narrator in shock. And then, his uncle transforms into a monster - a terrifying creature with rotting features and dripping claws. Desperate to fight back, the narrator activates the Crookes tube, but to his dismay, it proves ineffective. With no other choice, he flees through the cellar door as his uncle's body dissolves, morphing into the faces of those who perished within the house.

Undeterred by the horrifying events, the narrator devises a plan to rid the house of its malevolent presence once and for all. He procures a military gas mask, digging tools, and six carboys of sulfuric acid and arranges them near the cellar door. Resolute in his mission, he starts to excavate the earthen floor, unearthing a disturbing sight - a soft, blue-white, translucent tube. Realizing the monstrous nature of his find, he hastily retreats from the pit and pours four barrels of acid down the abyss. Overwhelmed, he faints momentarily, only to regain consciousness and empty the remaining two barrels to no avail. As he fills the hole back up and sees the once ominous fungus reduced to inert ash, he mourns his lost uncle but finds solace in knowing that the abomination has finally been vanquished.

In a surprising turn of events, the house later finds new occupants, unaware of its dark past. To their relief, the house now appears entirely normal, with no signs of the maleficent presence that once lurked within its walls. The narrator, although haunted by the events that unfolded, concludes his account with a mix of sorrow and gratitude for the newfound peace that has enveloped the shunned house on Benefit Street.