It all starts when Kourtney and her staff start noticing money missing and iPads disappearing. They quickly realize that the culprit has to be someone on the inside, working in the house.
"This lady stole $700 out of my wallet, then she stole $4,500 out of Scott's," Kourtney later tells her sister, Khloe Kardashian, of her and her ex, Scott Disick. "Then my security, who's here today, just said he's seen her two times with her flashlight on in the office."
Noting that she didn't have cameras in the areas where the woman was, Kourtney declares, "She's never coming here again."
"No s**t, Sherlock," Khloe replies.
Kourtney then reveals that the unnamed woman is at the house, adding that one of her assistants, "just pieced it together."
Kourtney is also informed that the woman is looking at her texts and has "hacked everything."
"Go talk to your security, why are you texting if someone's telling you that?" Khloe shouts, rushing her sister downstairs.
By the time the ladies get downstairs, they see a car screech off and begin angrily asking why the woman was allowed to leave. Khloe is shocked by how "passive" Kourtney is being about the situation.
Kourtney then tries to take action, telling her assistant, "We need to change the iTunes password, right now. We need to debug the house and I want to take every device and unconnect it from my phone. And next time, we've learned a huge lesson. They cannot step foot in here for an interview without us having their social, name, and address."
Scott Disick arrives to break down the situation, and Kourtney drops another bombshell.
"The fact that she was alone with our kids!" Kourtney says.
"This chick was nuts, man, but yeah, at the end of the day, at least she wasn't doing anything around the kids," Scott reassures her.
"I'm just happy she's out of here," Kourtney says.
The episode ends without the 40-year-old reality star locating the alleged culprit.
"I mean, just the police are doing an investigation and it's still moving," Kourtney tells Khloe and her mom, Kris Jenner.
"Did they go to her house? Did they find the money?" Kris asks.
"I don't know. I didn't ask. How are they gonna... the cash isn't marked, you know," Kourtney replies.
Khloe and Kris both seem shocked that Kourtney isn't more upset by the incident.
"I'm just moving on," Kourtney explains. "I don't dwell on things."
In an aside interview, Kourtney adds, "I obviously can't change what happened, but like anything in life, I believe that this is a big learning lesson... I just want to start fresh and get this bad energy out."
Naturally the ladies then decide to sage the house of the bad vibes left by the thief.
For more from Sunday's episode, watch the clip below: