The historic peace treaty, signed between the United Federation of Planets and the Cardassian Union in 2367, has so far failed to completely end hostilities between the two sides. Accusations of spying from the Federation, unrest in the Demilitarized Zone between Federation and Cardassian space, and the continued activities of the Maquis - considered outlaws by both sides - conspire to keep everyone on their toes.

On Stardate 44429.6, less than a year after the negotiation of the peace treaty, Gul Macet of the Trager and Captain Picard of the USS Enterprise watch in horror as the USS Phoenix, commanded by the renegade Captain Benjamin Maxwell, destroys Cardassian ships in a revenge attack; Maxwell`s family were killed during the Cardassian Wars. Although the Cardassians know Maxwell is acting independently, his actions do nothing to help already strained relations.

The following year the Cardassians try to dupe Starfleet officers Admiral Kennelly and Captain Picard into helping them destroy the Bajorans, a race they have oppressed and terrorised for decades. Picard saves the situation by tricking Gul Dolak into destroying what turns out to be an empty ship rather than a ship of armaments. This is hardly the kind of alliance anyone had in mind when peace was negotiated.

The unstable situation between the federation and the Cardassians comes to a head once again when Picard, Dr Crusher, and security officer Worf investigate reports that the Cardassians are developing biological weapons. The Enterprise falls under the command of the abrasive Captain Edward Jellico, an important figure in the 2367 peace talks, who is brought in because of his extensive knowledge of the Cardassians. Jellico manages to enrage Gul Lemec into admitting that the Cardassians know of Picard`s secret mission. Picard is captured and undergoes horrific torture at the hands of Gul Madred.

Some Federation personnel have the unique chance to see how things might have been, had history followed a different path, when Worf begins involuntarily jumping from parallel universe. All are more or less similar, but each also have their differences, particularly where the federation and the Cardassians are concerned.

In one universe the two races are allies against the warlike Bajorans, while in another the Argus Array has been sabotaged by the Cardassians for their own use. In a third, the Cardassians are merely curious about what the Enterprise is doing so close to their space.

One particularly troublesome problem created by the peace treaty is that of former Federation colonies which, once the new broders are established, find themselves in Cardassian space. One such colony is Dorvan V. On Stardate 47741.2 Gul Evek heads a Cardassian team that surveys Dorvan V, and comes into conflict with the Maquis, an organisation dedicated to opposing alleged Cardassian misconduct in the Demilitarized Zone. Frustrated by the Federation`s reluctance to interfere, the Maquis recruit many of their personnel from such worlds, and continue to be a thorn in the side of both the cardassians and the Federation.

Despite their perceived differences, in 2369 the Cardassians are one of the many races to learn that all humanoid species familiar to the federation are in fact related, through an ancient, advanced race that seeded the galaxy in the distant past.