In season 4, 'Downton Abbey' tries to stick to its knitting

Something about "Downton Abbey" died with Matthew Crawley last year. Oops -- sorry if you didn't yet know about poor Matthew, but honestly, how long must the rest of us keep quiet about it? Let's make a deal: This is a review of Season 4, which begins its American broadcast Sunday night on PBS stations. It will be necessary to mention one or two things that happen, but I promise to tread ever-so-lightly and somewhat unspecifically over the details. (Too late, you're gone. I completely understand...