"The Gateway of the Monster" is the first tale in William Hope Hodgson's Carnacki series, presenting a supernatural mystery recounted at a dinner gathering. Carnacki, a paranormal investigator, describes his investigation of a haunted room where multiple people have died under mysterious circumstances, employing both rational investigation and occult protective rituals to confront an unseen entity. The story combines gothic atmosphere with systematic, methodical approaches to the supernatural, establishing Carnacki's character as a figure willing to blend science and esoteric knowledge in pursuit of truth.