When a mysterious envelope arrives for Jake Ransom, he and his older sister, Kady, are plunged into a gripping chain of events.

Jake's new friends, the Mayan girl Marika and the Roman Pindor, say the creatures were created by an evil alchemist - the Skull King, Kalverum Rex.

According to Kirkus Reviews, Rollin's debut novel for children "starts out as a realistic thriller but takes a big left turn into fantasy without abandoning the thrills.

"[1] Publishers Weekly also highlighted the inclusion of non-fiction material, noting that novel "presents a wide range of interesting historical information while telling a rollicking good story".

[2] Booklist's Ilene Cooper compared the plot, as well as the main character Jake, to Harry Potter, but noted that "stylistically, [...] Rollins is no Rowling, though his short paragraphs and staccato sentences make this a fine read for the reluctant or those who put a premium on action."