Dissapearing Mac Mail


Average user.

My inboxes to the left will say I have 40 unread messages but they wont appear when I open that folder. Clicking on the folder only gives me the option to change its name. So the only e-mail I can read is what comes in, then that too dissapears next time I start up. This happened to 1 account right away and then the 2nd account a couple weeks later. I didnt change any rules, preferences, etc. It just happened out of the blue. At first when I noticed they were all gone I was able to hit "from" and they would appear, now they are gone no matter what I hit. My wifes account still shows her e-mails listed in the inbox but my other 2 are no where to be found. Where are the e-mails???????