Season 4
The command of the space station Deep Space Nine was supposed to be a low-key assignment for Commander Benjamin Sisko, who had recently suffered a personal tragedy.
However, the discovery of a wormhole leading to a previously unexplored region of space turns Deep Space Nine and its surroundings into one of the most important areas governed by the United Federation of Planets.
The third Star Trek series to be created, Deep Space Nine is the only one not be set on a starship, and is also notable for darker themes and more complex plotlines than its predecessors.