Six months after the Kur crisis, the other Secret Scientists have discovered that Zak is Kur, and are tracking him to take him into custody, forcing the Saturdays into a life as fugitives. To make matters worse, the Nagas are also after Zak, in hopes of making him their new leader. Meanwhile, Doyle and Zon go to England and have a run-in with Leonidas Van Rook (who had just had his buisness overtaken by Abbey) when looking for V.V. Argost, who has mysteriously disappeared.
The Saturdays fight to keep the Nagas and the other cryptids from invading the world. Meanwhile, Doyle, Zon and Leonidas Van Rook are still looking for V.V. Argost. Doyle and Van Rook seem to find evidence that Argost is dead. The Saturdays go to Hong Kong expecting the Nagi invasion to start there but turn out to be wrong. The Nagas are invading New York. After some encouragement, Zak stops the invasion and is saved by a mysterious black shadow. It turns out to be V.V. Argost who offers to (cryptically) teach Zak to better control his powers through Argost's show, Weird World. Zak accepts the deal, despite knowing that Argost is trying to somehow trick him. Zak also asked Doyle to find out as much about Argost's past as he can.
Upon learning that a cryptid has awakened after centuries of hibernating in the jungle, the Saturdays head to Mexico.
The Saturdays set a course for Greenland so they can search for an ancient Sumerian tablet, but the family is forced to take a detour to Australia when the airship gets infested by Bunyips by V.V. Argost.
he Saturdays learn about a sect of Indian sorcerers who were able to drive out the spirit of Kur in the past, and they attempt to find them, in hope that group can do it again. They learned that in order to drive out the spirit of Kur a ritual, using an artifact known as the "Flute of Gilgamesh", must be performed
The Saturdays return to their headquarters to retrieve tomes from Drew's library and are ambushed by Tsul 'Kalu, a cryptid whose hand now resides at the end of Zak's Claw.
Doyle and Zak help Fiskerton come to terms with his Lemurian heritage.
The Saturdays and Abbey go to the Allegheny Mountains to help with a problem caused by the cryptid Allegewi, but Van Rook's new apprentice shows up to cause trouble for the family.
Drew reunites with Doyle, Zon, and Van Rook in the Himalayas, where they hope to learn about the orange cryptid that was stolen by Argost. Meanwhile, Doc, Zak, and Fiskterton attempt to make a deal with the rest of the Secret Scientists.