January 4, 2012, in Egypt, it was a hot day. Although it is always hot in the desert, today was an extremly hot day. To cool off, a group of four kids decide to bathe in the Nile River. Shortly afting wading, however, one of the kids discovers a full skeleton of a strange animal on the shore. Thinking it is just a piece of trash, he throws it in the water, where it breaks into three parts. One of the parts glows blue and activates into a Rhinesuchus. Terrified, the children run to shore.
At Upsilon Dot, Z, M.D. is shouting at the B-Team for their failures in episode 1 and 3, while simultaneously reading the newspaper section about paranormal activity. While trying to shout his 50th (or was it 51,999th?) insult as the Beta Pack, he discovers a news article about a "sea monster" sighted in the Nile River. Although the article suggests it is a hoax, Z, M.D. correctly idenntifies it as a Rhinesuchus, a temnospondyl amphibian from the Permian of South Africa.
The B-Team succesfully arrive in Egypt, as the Rhinesuchus is terrorizing the land around the Nile. Shortly after, Mander finds and touches the Water Stone, glowing bright blue, meaning he now has the ability to control Water Creatures. Then Mursula summons Sister to try and attack the Rhineuschus.
Back at the D-Lab, Rex is doing research with Compy, when suddenly Compy's sensors detect a creature in Egypt! Rex teleports away, while Reese warns Rex he should wait for Zoe, not knowing that he was long gone.
Rex arrives just as the battle between Sister and Rhinesuchus is starting, and watches in awe as the two majestic creatures fight. Sister uses Volcano Burst at the temnospondyl, although 30 times her size, is defeated instantly. An awe-struck Rex tries to gets its fossil but is snatched by Mander, who then summons "Ryne" out to "impress" Rex. However, Rex is feeling the complete opposite and summons out George.
Suddenly, Ryne rears onto his hind legs and water tendrils spin around him, nearly drowning Rex! He was surprised! It was the Shockwave move card! In retaliation, Rex has George use Fire Cannon on Ryne, but he's too strong!
Then suddenly, Zoe appears! She and Dicky have heard of the Rhinesuchus and Reese has flown her here. She summons Dicky to her full size, and with a well-aimed Thorn Whip attack, defeats Ryne. However, Mander still caimed the card.
In compensation, Rex and Zoe alone will stay an extra week in Egypt, much to the annoyance of Max.