A woman on TikTok says a prank she played ended up saving a marriage after she caught a woman cheating on her husband.

Summer Fox overheard a woman in her office talking about cheating on her husband so decided to intervene.

She prank-called the cheating wife and tricked her into ending the affair. 

"I worked in a big office with women and there was a different office but still the same company upstairs," Fox explains in her video. 

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The woman in her office — dubbed Sally for the purpose of anonymity — said she was "having it off" with the "man upstairs."

They would sneak out to the back room of the office and would kiss and cuddle behind closed doors — both were married to other people.

The affair had been occurring for a while, and Sally openly talked about it.

Fox said it was "like she didn't give a s---, she had kids and everything."

Fox used a "prank call app" to get back at the cheating woman.

Fox decided to use a prank call app that uses automated voice lines already pre-recorded and chose to use the one of a woman finding out about an affair. 

"So, I decided that it would be really funny if I did the cheating one on the woman that was getting with the man upstairs," Fox explained — she was 20 at the time, and said she didn't know why it was funny.

Fox was sitting in the office where she worked and could see Sally's reaction as she answered the phone. 

She begins to ring Sally, and Sally answers, and the voice recording begins to speak, saying, "Who is this? I've seen your number on my husband's phone." 

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After the voice recording ends and Fox hangs up. In the office, Sally is distraught and panicking. 

"We're all watching Sally and seeing her react to it - and she's like, 'Who is this? Who is this?' She's panicking!"

She felt terrible that she was pranking her co-worker.

Fox said she was snickering and laughing cause she thought it was funny and then rang Sally again, and Sally answered — she heard the same voice and immediately hung up. 

She was wondering if Sally was going to call the man upstairs to come down and talk, saying they'd been found out.

At this point, Summer realized that she was in too deep and said in her video she needed to tell Sally.

"So, anyway, I had to say it didn't I? And I said, 'Sally, stop - it's just a prank call.' She started crying, and I felt so bad..." Summer said.

But Sally, instead of being furious, thanked Fox instead.

"Guys, I'm not actually p---d off, I've just realised how deep it is what I'm doing - I need to stop," Sally said.

Comments on her story have hailed her as an "accidental" hero.

Everyone on Summer's video has praised her for her actions in accidentally stopping Sally from going any further with this "man upstairs."

Thanks to Summer's prank, she inadvertently stopped the affair from getting any worse and, in turn, saved Sally's marriage.

Another reads, "Omg you're an accidental hero." 

"She didn’t think of the other woman! What goes around comes around," one user wrote.

Sometimes people are just in the right place at random times, but they can significantly impact others through their intervention.

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Kurtis Condra covers entertainment, news, and human interest topics for YourTango. He is also a poet based in San Francisco, California. You can keep up with his poetic journey on Instagram.