All Federation crew aboard Deep Space Nine begin to train for a possible infiltration by a Changling. Unfortunately, the DS9 staff is woefully unprepared as they have a hard time just tracking down Odo. As Captain Sisko spends some time with Kassidy Yates, an enormous contingent of Klingons arrive in their Birds of Prey to prepare themselves for the possibility of the Dominion coming through the wormhole.
s04e01 - The Way of the Warrior, Part I
s04e02 - The Way of the Warrior, Part II
s04e03 - The Visitor
s04e04 - Hippocratic Oath
s04e05 - Indiscretion
s04e06 - Rejoined
s04e07 - Starship Down
s04e08 - Little Green Men
s04e09 - The Sword of Kahless
s04e10 - Our Man Bashir
s04e11 - Homefront (1)
s04e12 - Paradise Lost (2)
s04e13 - Crossfire
s04e14 - Return to Grace
s04e15 - Sons of Mogh
s04e16 - Bar Association
s04e17 - Accession
s04e18 - Rules of Engagement
s04e19 - Hard Time
s04e20 - Shattered Mirror
s04e21 - The Muse
s04e22 - For the Cause
s04e23 - To the Death
s04e24 - The Quickening
s04e25 - Body Parts
s04e26 - Broken Link
When the Cardassian occupation of Bajor ended in 2369, the mining space station Terok Nor was left abandoned, its systems ripped out. By invitation of the Bajoran provisional government, Starfleet stepped in to oversee the rebuilding and day-to-day operations of the newly christened Deep Space Nine.
The years of Starfleet's nonintervention into Cardassian matters, however, had taken its toll on relations with the Bajorans. Consequently, Starfleet's position was a tenuous one; many Bajorans, suspicious and hostile as a result of decades of Cardassian oppression and brutality, did not greet the Federation's presence with open arms. The Federation's assistance is put to the test as DS9 becomes a center of travel and commerce that stretches into the Gamma Quadrant.