"Riddle of the Sphinx"
Season 3, Episode 4
Riddle of the Sphinx
Air date December 16, 2011
Written by James Felder
Directed by Seugh-Hyun Oh
Episode guide
"Phantom of the Soap Opera"
"Double Vision"
Images | Quotes | Transcript

Riddle of the Sphinx is the fourth episode of season three of Generator Rex and the 44th of the overall series. It debuted on December 16, 2011.


The gang goes to Cairo, Egypt, where strange EVO activity surfaces. Unfortunately, Black Knight has appeared to stop them from preventing her reaching the Sphinx's tomb.


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Holiday in the tombs.

Dr. Holiday is investigating an Egyptian tomb with the help of a guide who accidentally has activated the booby trap inside. Though she saves him from danger, the traps are not what he is afraid of. If legends hold true then the tomb was built to keep something in, not out. It has been several days since Dr. Holiday went to investigate the tomb and she has not yet reported back. Rex, Bobo and Six go looking for her.

They quickly discover that Providence is also investigating the tomb, and Black Knight and Robo Bobo have arrived in person to investigate. Rex accuses Black Knight of Dr. Holiday's disappearance, but she claims to have just arrived. Robo Bobo attempts to talk to Bobo but the latter simply tells him to lay low and keep an eye on Providence as planned.

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The group finds a back entrance.

Six takes the group to what he claims to be a back door, a restaurant manager who found the entrance while getting a water main repaired. The group enters the tomb and quickly find Dr. Holiday. She reveals that the tomb might not be as ancient as they thought, revealing the walls to be sprawled with nanite hieroglyphics. At first Rex believes that aliens built the tomb but Dr. Holiday states that none of the technology is more advanced than the 21st century.

Rex is able to use his powers to open the door and quickly discover the burial chamber of an EVO mummy. Black Knight arrives having discovered Robo Bobo and gotten the information she needed from him before destroying him. Black Knight is disappointed in the tomb having found nothing but relics of the dead, until she discovers that the mummy, Gharun Set, is still alive.

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Black Knight fends herself from Gharun Set.

At first Black Knight tries to reason with the mummy but when he starts spouting plans of world domination she tries overpowering him with a nanite disruptor. Not only is the device ineffective against Gharun Set but he has a far more effective version in his staff rendering Rex helpless against him. Gharun Set uses his staff to bring an army of similar undead EVOs to life. Though his first attempt fails miserably, he successfully awakens a legion of EVO mummy dogs.

While the group defends themselves from the EVOs, Rex goes after Gharun Set. Once on the surface Gharun Set brings out his trump card, the Sphinx which is revealed to be a tomb for a massive two-headed EVO carnivore. Gharun Set tries to rebuild his kingdom on top of Cairo using an antenna to amplify his disruptor.

After the EVO army spontaneously turns to dust Black Knight sneaks away. She discovers a nanite laboratory hidden in the tomb, though a booby trap and age has made trying to salvage the lab too dangerous right now and the group evacuates. In the meantime the same fate has occurred to the Sphinx and turned it to dust. Gharun Set's new pyramids also collapse, the result of 3000 years of age on Gharun Set's nanites.

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Gharun Set moments before dying.

On his death bed Gharun Set reveals that he intended to use the technology his "father" taught him to save the world from disease and war. Realizing Gharun Set is not as bad as he was led to believe, Rex offers to repair Gharun Set's nanites, but Gharun Set refuses to live in a world that he does not belong. Right before he and his steed turns to dust, Gharun Set reveals that his father knew both Rex and Black Knight very well and gives Rex a warning from his "father" to not trust Black Knight.

After Gharun Set's problem is resolved, Dr. Holiday demands Black Knight to let her study the tomb. Instead of complying to her wishes, Black Knight destroys the tomb and nanite lab with a bomb, much to Dr. Holiday's rage. When Black Knight leaves the the area, it is revealed that she took a section of hieroglyphs from the tomb, which includes a picture of Van Kleiss.


Voice Actor Role(s)
Daryl Sabara Rex Salazar
Wally Kurth Agent Six
Grey DeLisle Rebecca Holiday
John DiMaggio Bobo Haha
Robo Bobo
Jennifer Hale Black Knight
Rob Paulsen Pyramid guide (debut)
Bob Joles Egyptian cook (debut)


  • When they are fighting the mummy dogs, Six unsuccessfully attempts to tell Rebecca how he really feels about her.
  • It is revealed that Van Kleiss is somehow connected to the ancient Pharaoh, Gharun Set, and to Black Knight. This might be since Breach sent him randomly into another time, as seen in "Lions and Lambs". Later proven true in "A Brief History of Time".
  • This episode shares it's name with a video game called Riddle of the Sphinx.
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