A man on Reddit says his "crazy" sister-in-law insists his wife cheated on him with her boyfriend.

Content warning: Mentions of substance use

"So my wife had to travel to her step father's house. He is in very poor health, and she went there to help set up home health. She was there for a week, and we were in constant contact. Her sister is a drunk and a drug addict. At several points during the visit, we were on video chat when 'Shannon' came into the room where my wife and her father were. She was buck ass naked, raging drunk. In front of her father," he wrote.

"I was mortified, and I'm sure he was too. Now 'Shannon' is married, but separated. She has a live-in boyfriend. 'Tony' is my father-in-law's primary caregiver," the husband continued on Reddit.

READ MORE: ‘Ashamed’ Woman Has Been Paying Sister-in-Law to Keep Quiet About Affair

On the way home, the man's wife missed her flight after being driven by her sister's boyfriend to the airport.

"There was an unusual amount of road construction, and they arrived late. She had to take a different flight. Not a big deal. After she was home for a few days, the following text exchange happened between me and Shannon. Shannon: They f---ed. Me: Who, and did you film it? We could make a fortune on Pornhub! Shannon: I saw him leaving her room and smiling. You know she didn't miss her flight! He ain't denying it. Me: Well, if they did, he's the luckiest man alive," he recalled.

Although he knows in his heart that his wife didn't cheat on him, he is now upset that his sister-in-law put the "idea" in his head.

"So, the question: How do I deal with a crazy drunk 80 lb. woman from 1,000 miles away? I can't block her, because the rest of her family has. If something happens to the father-in-law while Tony is at work, I'm the only one she can contact," he shared, asking Reddit for advice.

READ MORE: Woman Gets Sister-in-Law Arrested on Her Wedding Day

Users in the comments supported the man and slammed his sister-in-law's ridiculous behavior.

"As unreliable sources go, she seems to check all the boxes. I would definitively tell your wife that her sister is trying to sabotage your marriage. Then both decide what’s the best course of action. I understand you completely trust your wife but seeing her reaction to the news could be telling," one person wrote.

"Personally, I’m inclined to think that if she was there for a whole week, it would be really stupid timing to start fooling around right before she has to head to the airport. She knew you were expecting her, and that she would have to explain her lateness. Also, if you were on the phone with her when she was driving to the airport, you know for a fact that they weren’t hooking up at that time," another chimed in.

"I think you handled it right, make like it’s a joke and continue to make like it’s a joke. Your SIL likely has no memories of most of your wife’s time there. She is perhaps conflating anger at her ex for cheating with guilt that he’s caring for her step father, and also lashing out at your wife for actually being helpful. She may have put the idea in your head, but you are the one who can turn it from a 'what if' idea into a 'wow, how disgusting is Shannon for trying to pull this little stunt' idea," someone else commented.

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