In "The Fix," Nick comes closer than he ever has before to a cure for his vampirism. This is the main plot point of the episode, and as such it makes for an extremely fun ride! Predictably, the would-be cure is only a temporary "fix," but much to the surprise of the viewer, it causes some other serious problems, as well. In the mean time, Nick and Schanke must determine whether or not a cop's death is a suicide or a homicide. The episode also follows the flashback formula where Nick is shown encountering trouble in the distant past which is relevant to his current situation.
The major drawback to this episode is that it is only one episode. It deserved at least two parts, and perhaps even a season-long story arc. Yet the writers in this case made a wise decision which helped make up for that limitation, launching right into the action and ending just after the climax. Because they didn't devote any running time to an introduction or epilogue, the episode is just long enough to develop the central story in sufficient detail. Just make sure you're paying attention from the beginning and not disappointed by a cold ending.