Part V is titled "A Nightmare and a Cataclysm". It concerns Dr Willett's investigation of the Pawtuxet bungalow and a horrifying revelation.
It is now clear to Willett and Mr Ward that there is a conspiracy of people who at least believe themselves to be necromancers from the 17th century, and who supposedly can recover the memories of ancient bodies from their "essential saltes". Willett and Mr Ward ready for an investigation to discover how deep into this conspiracy young Charles Ward has fallen.
In the bungalow they find a trapdoor leading to the secret laboratory of Ward/Curwen. The stench rising from this cellar is so unbearable that Mr Ward swoons and must be escorted away. Willett desires answers and so covers his mouth and descends.
Willett finds himself in a large vaulted cellar, surrounded by the overpowering stench and an ever-present howling that sounds as if it is coming from the ground. He wanders deeper until he comes across two carved pillars each bearing incantations evoking Yog-Sothoth. They appear nigh identical reverses of one another. Willett recognises one incantation as that overheard by Mrs Ward on that infamous Good Friday. He finds himself repeating the incantation under his breath.
Wandering ever deeper, he comes across an arrangement of pillars that draws to mind the image of Stonehenge. In the centre is a disturbingly carven and blood drenched altar. About this time he believes he can hear thumping coming from below.
Inspecting the floor, he finds hatches in the stone floor. Opening one he is horrified to see some "incomplete" body screaming and attempting to jump to escape. Willett is so shocked that he drops his flashlight, which the creature begins to eat. Willett then escapes in silence back to the bungalow.
Resupplying himself with light and steeling himself, Willett descends again and delves even deeper. He finally arrives at the laboratory of Ward/Curwen. lining the walls are several jars of powders, one set labelled "custodes" or guards, and the other labelled "materia" or materials. These names cause Willett to recall certain phrases from old letters and journals, bringing new disturbing meanings to them. He sees another door, bearing the sign of Koth above it, and recalls a discussion with his friend Randolph Carter. Willett passes through the door.
Inside, Willett is shocked to see a cup of powder and various tools of torture lining the wall. He is so shocked that he finds himself absently repeating one of the incantations. He sees the powder shifting and begin to take form, then passes out. He awakes in the bungalow in a bed. In his pocket is a note written in latin, roughly translated to "Curwen must be killed. The body must be dissolved in aqua fortis, nor must anything be retained. Keep silence as best you are able."
Willett and Ward go to the asylum confront Charles Ward once more. Willett reveals the horrors he found underneath the bungalow, only for Ward to take on a mocking and flippant tone. He mocks Willett further saying "had you known the words to bring up that which I had out in the cup, you had not been here to tell me this."
Willett now has the upper hand. He says that he did know the words and uttered them. He and Mr Ward leave Charles shocked. Willett hurries to the Ward home and investigates a hunch. He draws glasses and a beard on a photograph of Charles and realises that it looks very similar to Dr Allen. Other than one very early encounter, no one has seen Dr Allen and Charles Ward together.
The evening paper of the next day reveals yet more disturbances in the graveyard. No grave was disturbed this time. An unused plot had been disturbed by a trowel, the would-be gravedigger scared away by the watchman.
Mr Ward receives a letter from Willett, describing that Charles will "escape" from the asylum that night. That must remain their story. Once enough time has passed, he should erect a tombstone to Charles next to Mr Ward's father's grave, for that will be where he truly lies.
Willett returns to the asylum undercover. He confronts "Ward", saying that he found the body of Charles stowed away in the Ward home. The ashes of the body have been buried in the cemetery near a family plot. He knows of Curwen's sorcery to reach through time and compel a descendant to find and raise him. The infuriated and now revealed Joseph Curwen attempts to cast the same spell, only to be stopped by Willett speaking the reverse incantation, which will return Curwen to ash. Certain that the raised creature will take care of Curwen's associates, Willett's job is finally done.
Here we finally see the Dream Cycle mention. It seems that everyone in New England knows each other and just talks about dreams all the time. Dr Willett speaks to Randolph Carter of our previous tale, The Dream Quest of Unknown Kadath. Recall how Carter snuck through the city of the gugs and climbed the tower bearing the sign of Koth. Remember how a curse was placed such that the Gugs may not return to the overland of the Dreamlands. This gives us some clue as to the purpose of the sign of Koth placed in the secret laboratory.