Siege of the Bone Children

When his son dies in a terrible accident, Malcolm retreats behind the walls of the fort his son built, but those walls were more than a child's game, they served a purpose. When monsters begin showing up he realizes that when you hide behind walls to keep out the bad, you must always leave a door for the good. From the author of Asylum and The Collection, Erik Lynd, comes this supernatural horror story.
This story, along with others, is collected in The Long Fall Into Midnight Vol. 1