KUWTK : Kim and Khloé Kardashian Investigate Who Might Be Behind North West Parody Instagram Account

Kim and Khloé Kardashian are putting their investigative skills to good use.

In a sneak peek at Thursday's episode of Keeping Up with the Kardashians, Kim and Khloé team up to try and find out who is running the Nori's Black Book Instagram account. The page, which currently boasts more than 780,000 followers, is a parody account for Kim's eldest daughter, North West.

North, 7, is Kim's first child with Kanye West. The pair, whose divorce after six years of marriage was confirmed by PEOPLE in February, also shares three other children: Saint, 5, Chicago, 3, and Psalm, 2.

The clip opens with Kim, 40, and Khloé, 36, questioning celebrity hairstylist and family friend Jen Atkin via FaceTime about whether she's the person behind the account. "Are you Nori's Black Book?" Khloé asks, to which Jen laughs and then responds, "Oh, my God! I f------ wish I was Nori's Black Book. My captions aren't that good."

Khloé then notes that she and her cousin Cici Bussey "100 percent" believed that Jen was the culprit. Jen says, "You know who I think it is? … Steph."

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Trying to get down to the bottom of things, Kim promptly FaceTimes her former assistant and pal Stephanie Shepherd to see whether she's the guilty party. As Stephanie questions if she's on a four-way FaceTime call, the Skims mogul notes that they "have a serious question" to ask her. Khloé then requests that Stephanie "look Jen in the eyes" before providing her response.

"Are you Nori's Black Book?" Kim asks, leading Stephanie to reply, "Oh my God. I wish I was f------ Nori's Black Book."

After Kim ponders why "everyone" gives the same answer to the question, Stephanie theorizes that "it's someone random" who is running the account. "I don't think any of your guys' friends are that funny," Stephanie continues. "No offense."

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Khloé then agrees that "no one" in their circle boasts the sense of humor required for the funny captions, noting that she "would hang out with them all the f------ time" if so. From there, Kim suggests that the famous sisters call Tracy Romulus, who is the Chief Marketing Officer for KKW Brands.

"We've ruled a few people out of who it could be for Nori's Black Book," Kim says in a confessional. "We've called Jen Atkin, we've called Stephanie, Cici … we've tried everyone and they're all ruled out. So, I [am going to] call Tracy, who works with me, and she's, like, queen top dog investigator. Anytime we want to play a prank or do something, she always knows what to do and say."

During Kim and Khloé's FaceTime call with Tracy, the former Dash owners immediately ask whether she's behind Nori's Black Book. Once she denies it, she provides a potential solution to tracking down the account owner.

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"Why don't we try to contact them and say that we want to send them some KKW products," Tracy says. "Or why don't we just get their address and say we wanna send them a PR box?"

Kim notes that "that's a good idea" and "if this works, we might finally get our answer."

Ahead of this week's episode, Nori's Black Book promoted the clip on its Instagram page. "Uh-oh! Mommy and Auntie KoKo are trying to figure out who is 'Nori's Black Book,'" the caption reads. "They asked everyone they know, even Mason. Do you guys have any guesses???"

Keeping Up with the Kardashians airs Thursdays (8 p.m. ET) on E!