A woman revealed a "genius" investigation she launched to uncover her partner's deception in a video that has garnered over 6.4 million views.

"I used to be crazy,"  Alexandra Cooper, 29, the host of the popular "Call Her Daddy," podcast said. "I just want to put that out there, so there's no judgment. Yes, I was insane. But it was all in good fun."

Cooper said when she was in college at Boston University she was dating a guy from Florida, who at one point left his phone unattended, which she called "a woman's… dream."

Cooper admitted there are concerns about "privacy," but was undeterred. The opportunity is not one she could pass on. 

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Cooper's "Call her Daddy" podcast was part of a three-year exclusive deal with Spotify worth $60 million. (TikTok | @callherdaddy)

"I'm like, ‘I hit the mother lode, let’s f---ing go,'" she said. "A man's phone, unattended. Me, by myself with a man's phone. If I was a woman of God I wouldn't go through his phone. But I'm not. I couldn't walk away from this opportunity. And I don't know what woman could. Maybe if you're in a healthy relationship, but I wasn't."

Cooper explained the reason why, in this case, she couldn't stop herself from taking a peak.

"This man had been promising me, ‘You're the only woman that I'm talking to. I love you. I want you to be my girlfriend, Alex. I have not been with anyone else since we started talking."

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But the podcast host wasn't buying it. 

"I'm a lot of things," Cooper said. "I can be obnoxious. I can be passive-aggressive. But I'm not a f---ing idiot." 

But she was confronted with, not an ethical challenge, but a technical one.

"How do I guess this motherf---er's password?" she asked. 

Alex Cooper call her daddy

Alexandra Cooper and Alex Cooper (left) with Alix Earle (right) on August 22, 2023 in Miami, Florida.  (Getty)

Cooper, on her first try, typed in his Netflix account password

"And what do you know? We're in b----es!" she said. "I have full unrestricted access to his phone."

Cooper immediately searched his text messages. 

"Turns out he's not a man of God. He's a f---ing philanderer," she said. "This guy is texting so many women. Classic."

"And then I come across one of the most recent texts. And he doesn't have this woman's name saved. It's just a phone number," she said. At no point, however, did he mention her name in the text exchange – which complicated her investigation. 

Then, Cooper finds a damning piece of circumstantial evidence.

Her boyfriend said via text to an unknown girl, "You can go in the front door. It's unlocked. My bedroom is the one on the left. I'll be home in 20."

"Obviously, they're not meeting for a f---ing prayer group," Cooper quipped. "I kind of have proof."

This was the lead Cooper used to eventually snare her boyfriend with a smoking gun in his deception. 

"This woman was my best chance of cornering him and catching him in the lie that he hasn't been having sex with anyone but me for months," she said. 

Cooper dialed the number on her phone under *67 so the call would populate as "restricted" on the other woman's phone. No one picked up, and it went to voicemail which revealed the girl's name. 

Alex cooper call her daddy

Alex Cooper is the host of "Call Her Daddy." (Getty)

"Hey, it's ‘Kaylee,’ leave your message at the beep."

"Boom. I have her name," she said. Then Cooper scrolled through the messages and found a picture of the girl which indicated she was a bartender. 

Then the real investigative work began. 

"I go on Google and I search all of the Port St. Lucie bars in a 10-mile radius of his house," Cooper said. "I narrowed it down to seven contenders."

Cooper called each bar to try and narrow down which one of the bars had a girl named "Kaylee." 

"Hi, I'm really good friends with ‘Kaylee.’ I wanted to come in tonight. Could we make a rez (reservation) for four tonight? Is she working?"

Six of the bars said, "Sorry. What? Like a ‘Kaylee’ doesn't work here." 

Except for one. 

Alex cooper call her daddy

Alexandra Cooper is seen in Midtown on October 31, 2023 in New York City. (Getty)

"We got her name. We got the bar that she works at. That is enough information for me to concoct a brilliantly insane story to confront him about his lies," Cooper said. 

With all of her ducks in a row, Cooper was finally ready to reveal what she knew – but not her sneaky methods. 

She planned to claim she heard some information from a friend at Boston University who was friends with someone who lives locally, near the bar Kaylee worked at. 

"And so I look at this man and I say, …'I just got a text from my friend… saying that one of her friends lives in Port St. Lucie, was getting f----d up and hammered at her bar the other night, and the bartender she overheard was like bragging that she's f---ing you."

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"So I'm going to ask you a question. Did you have sex with Kaylee?," she asked her boyfriend. "Or is my friend just making all of this up? And she just got this information out of thin air."

Cooper's boyfriend broke down when she confronted him. She said he apologized and admitted to sleeping with Kaylee after she directly messaged him on Instagram. 

Cooper said it was one of her finest and most "genius" moments. 

"It's brilliant work. It's brilliant work by me. Because I never had to admit that I went through this man's phone. Then I'm in the wrong for invading his privacy. But no, I didn't. I just know people, a girl in [Boston University], knows a girl in Port St. Lucie, that knows the bartender that was bragging about you."

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Comments poured in praising Cooper's work, one with 15,300 likes calling her the "LITERAL FBI." 

"Being this toxic while wearing this dress is unhinged and iconic. It's brilliant work. I love it!," one comment said.