The latest episode of the US adaptation of "Doc Martin" airs tonight at 8 p.m. on Sky One. The story unfolds in the town of Port Wenn during its annual blueberry festival. A local man’s skin turns blue, leading to speculation that he may have overconsumed the fruit at the event. Meanwhile, the titular character, Martin, becomes concerned about the well-being of his Aunt Sarah, suspecting she may not be looking after herself properly. At the same time, Louisa sets her sights on winning first place in the festival’s pie contest, adding a competitive subplot to the episode.