So – you’ll probably be happier staying home. I’ll undoubtedly stay the night with my boss, so don’t wait up.
Your wife and your sister are long-time best friends, and what has you really worried now is that you know that your sister did not want your wife to marry you but instead she had wanted your wife to end up with her own husband's brother. She's been telling your wife how much happier she would be with your sister's brother-in-law almost from the day you two got engaged and you know that nothing would make her happier than leading your wife to eventually divorce you.