Sing along with this new Dexter ditty: “Dex and Debra sittin’ in a tree, K-I-L-L-I-N-G.” It’s odd, but while we know these are the final episodes for this show, it doesn’t quite yet feel like them. Plot lines, like Dr. Vogel’s abduction, still seem more like detours than a forceful march to the ultimate conclusion. But perhaps that will change tonight. Michael C. Hall, Jennifer Carpenter star – for a little longer.