War of the Cryptids.Argost starts his cryptid invasion of the Earth with himself leading an assault on Washington D.C. After the Saturday's arrive, a fight ensues. Zak goes to confront Argost where he tells him that he too has raised a cryptid army of his own with Wadi, Ulraj, Tsul 'Kalu and many more cryptid friends he has made throughout the show acting as de facto generals. Drew and Doyle join the fight and demand that Argost admit he killed their parents. The Secret Scientists then show up armed with an audio recording of the Flute of Gilgamesh which they use to hurt Argost and Zak. However Miranda Grey, not wanting to kill Zak, destroys the controls to Beeman's ship and Argost escapes with the flute recording. Having retreated to Weird World, he is confronted by the Nagas who pledge their allegiance to Argost. Argost then, on the Naga's advise, orders his army to begin massacreing the humans. The Saturdays once again invade Weird World where they begin fighting the Nagas. During the fight Argost appears and asks that Zak face him alone. However, Rani Nagi takes Drew's fire sword and tries to shoot her but Van Rook jumps in front of the blast and dies. Zak, realizing his family may also soon die, agrees to Argost's terms. Argost then surrounds himself with sound-proof glass and uses the flute recording to steal Zak's powers and transfers them to him which kills Zak. However since Zak Monday's powers are antimatter and Zak Saturday's are matter they cancelled each other out, causing Argost to be destroyed in a huge explosion. Zak then wakes up on the airship having been dead for a few minutes but revived by his parents. Everyone is overjoyed once they realize that since Zak's powers were cancelled out with Zak Monday's powers and that Argost was killed in the process the Earth has been saved and Zak's cryptid controlling powers gone. The episode ends with the Saturdays paying their respects at Van Rook's grave as a news anchorman reports on the incident saying global climate change is likely to blame and asks if the cryptids left either because they chose to or if the planet owes a debt to a group of unsung heroes.