Mouse discovers his diary, in which he documents his obsession with something called "The Green Book", his contentious relationship with his wife, and his own descent into madness.

When her dog, Bongo, leads her into the realm of the White People and their Effigies (the titular "twisted ones"), Mouse barely escapes with her sanity intact.

With the help of neighbor Foxy, a brassy, 60-something ex-hippie who lives across the road, Mouse re-enters the realm of the Effigies to try to rescue whoever is trapped there.

[6][7] Common praise for the novel centered upon the character of Mouse and the book's atmosphere and tension, with Starburst writing that "Like the best occult fiction, the novel’s building sense of unease comes from the unexpected, the incongruous and the unexplained.

[10][11] The British Fantasy Society's Sarah Deeming commented that "knowing that Mouse would be OK lost a bit of the tension", as this was detailed in the beginning of the book, but that "As an atmospheric, creepy read, The Twisted Ones has some great moments.