O filme e o romance são bastante próximos: ambos mantêm o mesmo estilo " frame story " (história dentro de uma história dentro de uma história) com o Expressionismo Alemão como uma ferramenta de filme para substituir o estilo de escrita original de Lovecraft (para que você tenha atores superando as emoções quando eles encontram "formas blasfêmicas, ciclópicas e sem nome que não poderiam existir!").
A história em ambos os casos é quase idêntica com poucas diferenças:
The sailors aboard the Emma first encounter the Alert abandoned at sea, rather than crewed by Cthulhu cultists and taken over by Emma's crew after a violent confrontation as in the original story. Additionally, the film depicts the narrator present at the time of his great-uncle's death, who dies peacefully in his sleep, rather than being summoned upon the mysterious death of his great-uncle, who was presumably killed by Cthulhu cultists in the original short story. The narrator (Matt Foyer) notes that Inspector Legrasse, who had directed the raid on cultists in backwoods Louisiana, died before the narrator's investigation began.
In the original story, the narrator does not seem to end in a lunatic asylum or experience any mysterious nightmares himself. source