For Mother's Day, Homer takes the kids with him on a Krusty day cruise, giving Marge the day off.  Once the cruise takes off, Homer, Reverend Lovejoy and Apu all get a letter addressed to them from Moe telling them he plans on running off with one of their wives.  After a series of flashbacks showing each of the unhappy marriages, it turns out Moe ends up fixing all three of their marriages.