In The Terror it is Dr Lewis, a country practitioner in southwest Wales, who hits upon the explanation of a large series of mysterious and seemingly unconnected deaths. The animals have revolted in concert against the overlordship of mankind: placid dogs turn savagely on their owners, bees sting people to death, sheep drive walkers over cliffs and down quarries, cows trample farmers into marshes, moths form immense clouds that suffocate children to death, and flocks of birds fly into the path of aeroplanes and cause them to crash. The story was written in 1917, when the slaughter of the war deprived humanity of its right to call itself superior to any beings whatsoever.

In so far as Machen is remembered, except by the coterie, it is for originating, by means of a story published in 1914 in the Evening News, the myth of the Angel of Mons, according to which bowmen from the Battle of Agincourt were seen protecting the British army from superior German numbers. What started as fiction became accepted fact for a surprising number; apparently it helped the recruitment drive.

In his stories, Machen is unable to decide on the precise relations between the material and immaterial, the physical and the mental—just like us, really.