TNG Season 4 Episode 12: The Wounded

A veteran Captain of the Cardassian/Federation War, Ben Maxwell has taken it upon himself to launch his Nebula class starship, the USS Phoenix, into a one-ship war against the Cardassian Empire, believing that they are rearming to challenge the Federation once more. A Cardassian Gul (Captain) and two aides join the crew of the Enterprise to stop the Phoenix destroying further Cardassian vessels and outposts.
This is the first appearance of the Cardassians on screen with Marc Alaimo staking an early claim to the de-facto portrayal of a Cardassian commanding officer, Gul Macet, in advance of landing the regular role as Gul Dukat in Deep Space Nine. We also learn a bit about Chief O’Brien’s background in the process – giving Colm Meaney some decent room to show what he can do.

Plot

While patrolling near Cardassian space, the starship Enterprise is suddenly attacked by a Cardassian vessel. Captain Picard (Patrick Stewart) is able to convince its commander, Gul Macet (Marc Alaimo), to stand down, and learns that Macet's attack was in retaliation for a Federation ship attacking a Cardassian science station two days prior. Picard confirms this with Starfleet, and is told that the starship Phoenix, commanded by Captain Benjamin Maxwell (Bob Gunton), was responsible, and ordered to locate the vessel. Picard invites Gul Macet and two of his officers to come aboard as observers to maintain the fragile peace between the Federation and Cardassia. As the Enterprise looks for signs of the Phoenix, Picard discovers that transporter chief Miles O'Brien (Colm Meaney) was a former crewmember under Maxwell on the Rutledge during the Cardassian war, and invites him to join a briefing with Gul Macet. There, O'Brien reveals he still harbors some resentment for the Cardassians, revealing that Maxwell's family was killed by Cardassians. Gul Macet infers that Maxwell must be out for revenge, but O'Brien denies this.
The Enterprise locates the Phoenix on an intercept course for a Cardassian freighter, but they will not be able to reach it in time. Picard lets Gul Macet relay the position of the Phoenix to a closer Cardassian cruiser, but Maxwell outmaneuvers and destroys both the warship and the freighter, killing over 650 Cardassians.
Shortly thereafter, the Enterprise rendezvous with the Phoenix, and Maxwell transports aboard, greeting O'Brien as an old friend. Alone, Maxwell asserts to Picard that the Cardassians are re-arming themselves; the science station was a cover for a military base, and the freighters are carrying weapons. Picard admonishes Maxwell for his behavior unbecoming a Starfleet captain, and gains his assurance that he will pilot the Phoenix directly back to Federation space. However, en route, the Phoenix breaks course towards another freighter. Maxwell is poised to destroy the freighter, demanding that the Federation officers be allowed aboard to see proof of the Cardassians' deception. The Enterprise crew notes that the freighter is equipped with a field that blocks their scans. Picard prepares to fire on the Phoenix to maintain the peace, but O'Brien requests permission to beam over to the Phoenix, using a transporter trick to sneak past its shield, and talk to Maxwell. Aboard the Phoenix, O'Brien and Maxwell reminisce about their time aboard the Rutledge and sing a song from their past. O'Brien is able to convince Maxwell to stand down. Maxwell transfers his command to his first officer and the Phoenix starts its return to Federation space, while Maxwell returns to the Enterprise with O'Brien, to be held there pending return to Starfleet.
As the Cardassian observers are returned to their ship, Picard cautions them that while Maxwell's actions may have been improper, his suspicions are not without merit; the so-called "science station" is located in a strategic military position with little scientific value, and the shields on the freighters were specifically designed to block Federation scanning. He cautions Gul Macet that the Federation will be watching the Cardassians very closely in the future.