The main character, Martin Behaim, wakes up in a house without doors or windows. There is a fully stocked larder and kitchen and a library featuring all the books he enjoys, as well as a television and a computer (though every page except for Blogger is blacked out). On the computer is a note: Write or the Shadowmen will come.
After a few days, Martin starts to go a little crazy. He finds another blog called the allegory of the cave which leads to another blog called Out of the Spent and Unconsidered Earth. Finally, he refuses to write at all in the blog and then, at night, he is visited by the Nightlanders. The Nightlanders create a shadow play for him to explain about the Fears (though he still doesn't understand anything) and then when they leave, he finds a book left on his bedside table: The City on the Borderland by William Hope Hodgson.
Martin begins reading the book, though it is hard to slog through all its purple prose; however, the book describes an everchanging city and "Doorways into Night" which lead to this city. The main character of the book eventually tries to escape and does so, but ends up wandering the "Night Lands." Martin doesn't know what to make of it, especially the inscription in the front of the book: To Martin - W.H.H.
Finally, a Door appears in the living room of the house and Martin has to decide to go inside or not. Finally, he does and leaves for five days. On the fifth day, he returns and reveals that the Door lead to a long hallway - an infinite hallway, actually, since he couldn't reach the end at all. Finally, another Door appeared in the hallway and he returned back to the house. Martin starts to despair that he will never escape.
Soon after, Martin has a dream that he enters a Door and goes back in time to meet William Hope Hodgson before his death at the Battle of Ypres. Hodgson signs The City on the Borderland and gives it to Martin and Martin goes back in a Door and leaves it on his bedside table during the shadow play. Then he goes back to one of his memories of childhood, his mother singing to him, and he has a revelation that the Martin in the memory isn't him - he is just a shadow on the wall.
Martin gets a phone call seemingly from himself - and then somehow remembers walking through a Door and going into the Empty City, even though that appears to be a different Martin. Finally, Martin reveals that he was never Martin at all: he was always a Nightlander. This was all just a way to show him that escape from the City was futile and the City was chaos, so order is much better.
The blog ends with "Martin" returning to the other Nightlanders and reordering a person's house and mind. He then leaves a page from The Monster at the End of This Book from the real Martin's memories, a page that he had blacked out with a crayon.