Read prequel The Angel Knights first.

When teens go missing in Hawaii, a group of demon-hunters - half human and half angel - disguised as high school students, must leave Crossroads, the place where they reside. In a race against time, they uncover the mystery connecting the missing teens, which dates back to the era of the Knights Templar. However, when they discover one of the Templars passed down a book containing all the secrets and codes to finding a particular treasure, they soon realize this forbidden treasure needs to be found before Cyrus, the lord of the possessor demons, acquires it - a treasure which been safeguarded and hidden from him.

There is only one problem: the pages containing the clues leading to the treasure are missing. When the first page is found, Cyrus threatens to kill more descendants of the Knights Templar if it is not given to him by Friday the 13th. In the midst of threats and discovery, the demon-hunting angels find they are not alone when supernatural beings begin to reveal themselves. Can they put their differences aside and work together to solve the Knights Templars' cipher? As they astral travel to the past, they witness a lot more than they have bargained for. And some things are better left unseen.