S1:E13: Dear Doctor: The Enterprise crew meet an alien species stricken with a sickness that is killing their race and is asked to help find a cure.
When an alien species requests help from the Enterprise crew in hopes of curing an epidemic in the world of a pre-warp civilization, Dr. Phlox works diligently to find the cause of the sickness. When it is discovered that the sickness is actually a genetic defect that is causing the pandemic, the whole premise of the episode becomes the moral ramifications of playing God: Do we help because we can? And what kind of repercussions could come to be if we do?
The majority of the episode is shot from Dr. Phlox's standpoint and is loosely centered around letters between him and a colleague also enrolled in the Interspecies Medical Exchange. Phlox's internal narration gives us an interesting view from an alien perspective on his admiration towards humanity's compassion and willingness to help others whom we didn't know even existed just days before. We're also treated to the story of Phlox's budding romance with Crewman Cutler.
Also, in a number of these early episodes, it's fun to see Ensign Hoshi Sato interacting with both Dr. Phlox and T'pol as she works to perfect her interpretation skills. While her interactions with T'pol are rightfully much more rigid, alternatively, her conversations with Phlox make for some great comedy, such as when she tells Phlox (in Denobulan) that she thinks Phlox and Cutler would make a cute "washboard", or how when talking about food, she explains to Phlox that eggplant was actually not a vegetable, rather it is a "nostril".