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.

Doyle and Zak help Fiskerton come to terms with his Lemurian heritage.

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.

Upon arriving in Antarctica, V.V. Argost releases Kur from beneath the ice. The Saturdays battle against Kur, giving Argost the opportunity to sneak inside its body and control it from within. Zak follows Argost inside, pitting his powers against Kur's might. After a long struggle, Zak manages to overcome Kur, knocking it unconscious. The cryptids formerly under Argost's control turn on him, forcing Munya to carry him out to safety. Outside of Kur, Doyle uses the Kur-sensing relic to solidify the point that they are near Kur. However, once Zak is expelled from Kur's body,the glow began to fade. Doyle approaches Zak, and the artifact glows strongly once more—showing that the Antarctic Cryptid wasn't Kur, but that Zak is actually Kur.

The Saturday family call on the para-neurologist Dr. David Bara to find the motivation behind Fiskerton's strange instinctual behavior, while V.V. Argost sends a Neural Parasite to the Saturdays' home to extract Kur's location from the creature's brain by force.

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.

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.

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.

After disturbing an Inuit chamber, the Secret Scientists accidentally create a giant snowstorm. Along with this snowstorm comes a creature known as an Amarok.

With two of three Kur Stone pieces now in V.V. Argost's possession, the Saturday family races to the location of the final stone piece, Manaus, Brazil before Argost can get to it.

The Saturdays discover a "Bigfoot" like creature in Japan who wants revenge on his creator.

When Zak and Doyle go on a training mission in an abandoned town, they make a surprising discovery.

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.

When Zak finds out that a cryptid hunter plans on attacking their headquarters, he comes up with a plan to save the day without ruining Doc and Drew's anniversary.

V.V. Argost, host of the popular TV show, Weird World, is after the legendary Kur Stone, which is capable of unleashing the powerful ancient Sumerian cryptid, Kur. With it, V.V. Argost plans to rule the world, so it's up Doc, Drew and Zak Saturday to stop him.

V.V. Argost becomes the new king of an ancient, sunken city that has been resurfaced.