PBS wants its own hit drama, but 'Mercy Street' lacks more than just a British accent

The slight sense of longing that runs through the six episodes of PBS's utterly average Civil War drama "Mercy Street" is not about the characters' wants and desires or the ample metaphors evident in a tale of disunion. All a viewer can feel here is that PBS wants to be dealt into the high-stakes game of Peak TV, but on its own terms.