Captain Obvious Reveal: "Akeley" isn't who he says he is after the real Akeley's final encounter with the Mi-go and their human allies. The complete change in his character and how he writes to Wilmarth, using a typewriter instead of writing by hand, make it clear that it's some kind of imitation. This does preserve what really happened to him until the end, though.
Complete Monster: P.F. Noyes, an enigmatic Bostonian gentleman who greets protagonist Albert Wilmarth in his trip to Vermont, is actually the leader of a cult dedicated to the extraterrestrial Mi-go. Noyes lends his full aid to having loose ends murdered by the Mi-go and luring those too much in the know—like Henry Akeley, and Albert himself — to extract their brains and keep them locked away in jars for the Mi-go's uses. Noyes fully intends to let the Mi-go gain passage to Earth and doom humanity in the process, all for the sake of the knowledge he'll gain in return, and tortures one of the people the Mi-go have kept in jars when he expresses horror at this, up to the point where his brain is agonizingly burnt out.
