After the necklace of Osiris is stolen, Isis and Hercules investigate. They soon find that the wizard Thoth plans to conquer the Nile valley with his plant soldiers, and they must stop them with the help of Super Samurai.
At the Valley of Time, Isis and Toshi are playing tag, and Toshi hides in the Hall of Treasures, and Isis multiplies herself into three people so that she can find him quicker she eventually locates his hiding place. Just then, Hercules comes in and asks where everyone is. Isis calls out to him and tells him they are right next to the Necklace of Osiris. But when she turns she finds that the case had been shattered and the necklace stolen. Isis tells Toshi to find Merlin, while her and Hercules scout the area.
Hercules is riding on Pegasus while Isis is flying beside him. They fly off and scout the area and arrive in Egypt. There, men are hard at work building a pyramid, and one of the slave workers calls out "Water, water, we are thirsty!" But the Water Handler tells him that they have used up their ration for the day, and the water has ran out. The slaves all begin to collapse from dehydration, which causes them to drop the giant pyramid block, and it slides down the dune hill about to smash into King Ras. Isis then rescues the king. The King offers to reward them for saving him but Isis tells him his safety is a reward enough for her. Hercules asks why the workers are so tired. And he shows them that the Nile River is completely dried up. Isis is certain that it must have been the person that stole the Necklace of Osiris that caused the disaster. They then trek up river, and they see that there's nothing but dry river bed. But as they proceed further up river, they hear what sounds like running water.
They follow the sound, and come to find that the river had been stopped up by some sort of an invisible dam, to which King Ras states must be the work of a very powerful wizard. They take a closer look and find a farm and that the stolen water is being used to irrigate it. Isis and King Ras go together, and Hercules tells him that he will circle around the farm and meet them below. Isis notes that there's something very creepy about the plants, and that she's never seen anything like them before. Just then, the plants start to attack Isis and captures her, King Ras runs away and promises her he will find Hercules. She is then taken to the palace of Thoth, where she sees that he is wearing the Necklace of Osiris. He tells her his name, and that he is the ruler of the Plant Soldiers, and soon to be the ruler of the entire Nile, once he has conquered the lower valley. He then uses his magic to encase Isis in a cage that cuts her off from all of Earth's natural elements.
Meanwhile, after King Ras finds Hercules, he leads him and Pegasus to where the Plant Soldiers had taken her. They then release Isis from her glass prison cell. Isis tells Herc and King Ras to go after Thoth while she undoes the magic that he used to dam up the Nile. After undoing the magic, the river rushes forth, and plunges into Thoth and his army, and causes him to lose the Necklace of Osiris. Hercules then grabs hold of it.
Later, back at King Ras's kingdom, he thanks the Freedom Force for saving his kingdom, and asks what he can do to repay them. They tell him that the Necklace of Osiris being back where it belongs was repayment enough. Hercules asks if the construction of the pyramid will continue, and he says no. Instead, they are working on building a dam, so that next time they will be prepared when they lose their water supply. And as for Thoth, he was given a job of working with plants. And the Freedom Force laugh as they watch him pricking himself on sharp thorny vines.