After battling a supernatural sleeping sickness that early claimed two of their own, the Diviners have had enough of lies. They're more determined than ever to uncover the mystery behind their extraordinary powers, even as they face off against an all-new terror. Out on Ward's Island, far from the city's bustle, sits a mental hospital haunted by the lost souls of people long forgotten--ghosts who have unusual and dangerous ties to the man in the stovepipe...

When Samuel Johnson and his dachshund Boswell go trick-or-treating early, they unwittingly unlock a gap in the universe that opens the gates of Hell, and Samuel must now fight to reseal it.