In the Mouth of Madness

Horror author Sutter Cane has gone missing, and his work is spreading an epidemic of violence across the world. John Trevor is an insurance investigator hired by the publisher to find Cane, which takes him directly into Cane's world and work, and exposes the forces outside our reality that are shaping it. This John Carpenter classic is a love letter to Lovecraft, and you should absolutely watch it.