Here is my evil plan.
Buy another identical diary. Replace the one in the drawer with the fake. Your wife has already read it and won’t look at it again soon.
Invite sister and BIL over for dinner.
Put the real diary on a bookshelf in the living room.
Make sure he sees it during the course of the evening.
Try this. Get a very, very sharp knife. No, don’t kill anybody. Get the diary, and carefully remove every other page. Replace in underwear drawer.
Now, the first question that you have to ask is: How did the diary, physically, get into a position for your wife to receive it? That will answer many of your questions.
Best wishes,
hh
When were the accusations of the initial affair? If it was during this time period, I would find this diary suspicious. It’s almost like an alibi intended for you to see it…
Hm. In the OP’s shoes, think I would helpfully return the diary to my sister, saying BIL’s lost diary has been found. When sis says “Where did you find that?” answer honestly with eyes brimming full of naive innocence.
But what I would want to do is the suggestion of hiding it from her and not saying a thing and/or letting Sister in on it. It will make Wife crazy on a number of levels, she’ll probably tell BIL that it’s missing, and then they’ll both worry about who knows what.
I can’t decide which of these I like more. I think hiding it seems more subtle and a little more likely for her to all paranoid. “Like…wait, does he have it or did I just put it somewhere else or…?” Yes, I think hiding it is truly the more evil.
Hiding it only lowers yourself to their level. Open and honest confrontation is the best way to go. But I would definitely call the BIL first. Probably would do it while the wife is home and in the other room, so that you could immediately go talk to her after you get off the phone with BIL, so the two couldn’t have a chance to match up any stories.
I’m not sure what there is to confront them about if there is nothing incriminating in the diary. The most likely explanation is that the brother in law had the diary with him at some point when he visited the house and just left it or dropped it. Now, if the OP doesn’t know about his brother visiting the house around the time the diary entries stopped, maybe there’s an issue.
The first possibility that came to my mind was that your wife had stolen the diary. If she is missing/looking for that “zing” of feeling wanted/desired, she may have stolen the diary hoping to find rantings about how much he wanted her in there. Having been cruelly disappointed by the mundane contents, she tucked it away intending either to destroy or return it.
Whatever else has/hasn’t happened, I’d say BIL has lost substantial footing here by not feeding her want/need. I agree with the above suggestion to check for signs of missing pages. But it sounds to me like it was never that sort of diary.
Re: PYD
Inquiring minds would like to know how it could be such a mistake to read one page? Either you found out something that horrified you (thus alerting you to the need to end the relationship) or you found out something which disappointed you (thus alerting you to her need to end the relationship.) Either way, isn’t it better to know? I would much rather be in Hell with the truth than in Heaven with a lie. I just can’t think of a scenario where you learned something important enough to give sucha reaction, but which you’d be better off not knowing. . .