It takes a special kind of oblivious for the Miami Police Department to have gone this long without realizing their resident blood splatter expert is actually offing people all over the place, but for his own sister to not know is ridiculous, especially when her dad trained Dexter to kill when they were both kids. She must have been standing all alone in the back yard eating ice cream or something while they went through drills in the basement.
This season even added a little adopted-incest (which isn't as bad as the real thing, but c'mon) to her repertoire. You don't have to be a moron to fall in love with your brother. You just have to be a television character on an increasingly hard to swallow drama. Few characters have been as frustratingly moronic as Deb. And now that she knows Dexter's big secret, you can bet her reaction will be slightly less than smart.
