The Son of Sobek is a short story told by Carter Kane in the paperback version of The Serpent's Shadow with a guest appearance by Percy Jackson. Rick Riordan announced in February 2014 that the sequel would be titled The Staff of Serapis.
In this story, Carter Kane is investigating rumored sightings of a monster on Long Island when he is taken by surprise and then runs into something else: a mysterious boy named Percy Jackson, who is trying to stop the beast as well. And their meeting in the swamp turns nasty after magical terms get out of hand...
A huge crocodile has been terrorizing Long Island, along with other magical disturbances in the area. After being alerted by other members of the House of Life, Carter Kane takes his pet griffin, Freak, to go survey the area. After settling down on the ground, Carter is left behind as Freak flies away with his floating boat. Forced to find the monster, Carter goes into a lake to start his search. Suddenly, the crocodile comes from underwater and swallows Carter whole. Set on destroying the creature, Carter plans on using a "word of power" to escape when the crocodile spits him out after it is jabbed in the rear end by Percy. The crocodile soon runs away.
Carter picks himself up and sees the other teenager in the mud. The boy is wearing an orange T-shirt that says Camp, but the rest is unreadable. As Carter examines the "camper boy," he soon realizes that he can clearly see his wand and khopesh, something most mortals are unable to see. He also notices the strange sword that the teen carries, which is a double-edged bronze blade. Despite meeting almost all magicians in the North American Nomes, Carter has no idea who this person is, only that everything about him seemed "un-Egyptian."
The teen tries to get Carter to thank him for rescuing him from the crocodile, but Carter is somewhat embarrassed and ends up getting angry at Percy's comments instead. The two then get into a small argument over the ownership of the monster, with Percy thinking that the monster is Carter's pet after he said it was his monster, but only meant he was chasing it. Percy then asks Carter if he is a son of Ares as he must be a half-blood of some kind. He also asks why his sword is all bent, but Carter tells him it is supposed to be like that. Carter also gets angry at Percy's use of the word Half-Blood (as his dad is African-American and his mom is white), as well as Percy offering to help because last time Carter was eaten by the crocodile.
After being offended by Percy, Carter accidentally uses the "Fist of Horus" out of anger to cause a fist to knock Percy literally right out of his shoes and into the swamp. Carter instantly rushes over, thinking he might have killed Percy, but is taken aback when he is hit in retaliation by a huge wave of water. Taking the fist as a challenge, Percy furiously lunges at Carter with his sword and Carter is forced to defend himself, not able to attack because of Percy's skills with a sword. During the ordeal, Percy accuses him of being a monster, which Carter says he isn't. Percy also asks if he is an escaped spirit from the Doors of Death or if the monster was his pet and Carter was just trying to find it. Carter is confused by all of these comments, which are referring to Greek mythology, which Carter is unfamiliar with.
The fight ends when Carter uses some magic rope to tie Percy's sword to his head just as Percy hits his arm, causing Carter to be wounded badly. During the short aftermath, Percy comments that Carter must be a half-blood because if he wasn't, his Celestial bronze sword would have passed right through him. Percy also asks if he was a rogue demigod who used to be part of Kronos' Army. After listening to Percy talk for a bit, Carter starts to realize that Percy isn't a magician and is something completely different, as Percy keeps using words related to Greek mythology. The two form a truce so that they can go after the crocodile, as it has been terrorizing Long Island for weeks now. The two also introduce each other, eventually revealing their names grudgingly.
They eventually find the crocodile attacking a small subdivision cul-de-sac with a few kids attempting to defend themselves by spraying the monster with water guns and throwing water balloons at it. Carter sees a gold necklace around the crocodile's neck. He realizes that the necklace is controlling the crocodile and tells Percy that they need to remove it to stop the monster, as it can't be killed since it is immortal with the necklace. Percy tells Carter to distract the crocodile so that he could get it. Carter forms the powerful avatar of Horus the Avenger around himself (which Percy calls a giant glowing chicken-man, oblivious to Carter's distress) and attacks the monster. Percy then jumps on the crocodile and tries to unlock the necklace, but can't as he isn't an Egyptian magician and cannot find a way to. As Carter's avatar fades and the crocodile crashes into a house, Carter and Percy recalibrate their plan with Carter attempting to loosen the necklace. Percy creates a massive hurricane in the center of the cul-de-sac using the water generated by the beast. The crocodile is swept up in it and Carter manages to make it to the necklace. As Percy begins to collapse from too much magic, Carter finally manages to remove it by punching the third symbol and the crocodile returns to its original form; that of a baby croc.
Percy and Carter run off with the baby crocodile after hearing some cop cars approaching. Taking shelter at a nearby diner, Percy and Carter watch the news, as they report that a freak sewer incident had destroyed the homes in the cul-de-sac. Carter and Percy wonder if someone is trying to bring them together to cause trouble and agree to keep their respective worlds a secret from each other until the time is right. Carter takes the necklace and the baby crocodile with him but plants a spell on Percy so that if he ever needs to contact him, all he has to do is say his name. The two part on good terms, but Carter feels that someday in the middle of the night, he'll wake up to the sound of Percy calling out his name. He begins to have an uneasy feeling that their meeting wasn't coincidental but is ready to fight with Percy should they meet again.
- The audiobook is narrated by author Rick Riordan; it was the first time he has ever narrated the entire audio for one of his own stories.
- The short story is a bonus feature with the paperback version of The Serpent's Shadow.
- The independent e-reader version of the story was released on June 18, 2013, along with a sneak peek of The House of Hades.
- Percy accuses Carter of being an escaped soul from the Underworld who used the Doors of Death and as a former member of Kronos' Army.
- The worlds of the Kane Chronicles and the Percy Jackson and the Olympians series have only crossed paths once before, when Drew Tanaka and Lacy, both demigod daughters of Aphrodite, appeared in The Serpent's Shadow. Incidentally, they both met the Egyptian god Anubis at that time, albeit unknowingly.
- Riordan later released the sequel, The Staff of Serapis, which features both Sadie Kane and Annabeth Chase meeting and battling Serapis, a Greco-Egyptian deity.
- It is revealed in The Staff of Serapis that using the Book of Thoth, Setne created the necklace that transformed the crocodile, so he is responsible for Percy and Carter finally meeting.
- In this story and the subsequent crossovers, the narrator strikes the final blow to the antagonist:
- The Son of Sobek: Carter unclasps the petsuchos necklace, reverting the monster into a baby crocodile.
- The Staff of Serapis: Annabeth stabs the staff, destroying Serapis's power and the god.
- The Crown of Ptolemy: Percy hosts Nekhbet and defeats Setne, then forces him to regurgitate all of the magic that he had absorbed.
- The Battle of Montauk is blamed on a sewer explosion. Percy notes how a battle being blamed on a sewer incident is a first for him but Carter tells him that its not for him. This refers to The Throne of Fire where the Battle of Brooklyn House was blamed on sewer gas.