Picard contacts Admiral Haden, who says that the news is true. The starship in question is the Phoenix, commanded by Ben Maxwell, a fine officer. Haden tells the Enterprise to find him and to preserve the peace, no matter what the cost. He also, to soothe Cardassian nerves, takes on board Gul Macet and two aides as observers, despite distrust from some members of the crew...particularly O'Brien, who served with Maxwell years ago aboard the Rutledge, and saw a massacre which, among other things, took the lives of Maxwell's family.
Before long, the Enterprise locates the Phoenix- but long-range sensors find that the ship is about to attack a Cardassian supply ship. When Maxwell repeatedly refuses to answer Picard's hail, Picard is faced with no choice but to accede to the Cardassians' wishes, and he gives the Cardassian warship (which is much closer to the Phoenix) the Phoenix's prefix codes.
Despite this imbalance, however, the Phoenix destroys both the warship and the supply ship. As the Enterprise speeds up to intercept, Picard talks to O'Brien, who is convinced that the Cardassians are somehow at fault, not Maxwell. Picard points out, however, that Maxwell's been angry for so long that, although he may not consciously be acting on revenge, the anger has become "comfortable", and he may not be able to think around it. O'Brien soon realizes that he has the same problem, because due to the Cardassians, he was once forced to cold- bloodedly kill one.
After Worf brings in one of the other Cardassians, who was caught trying to access weapons information and is confined to quarters by Gul Macet, and Macet and Picard talk privately, convinced that a lasting peace is possible, they reach the Phoenix. Maxwell beams over, and seems friendly enough (particularly to O'Brien, not surprisingly). When he talks to Picard, however, it's a different story.
He claims that the Cardassians have been arming for war again, and that the ships and station he destroyed were all on military missions. He dismisses Starfleet as too bureaucratic to have done any good in the situation, and when Picard refuses to condone his actions, brands Picard a fool. Picard, not allowing Maxwell to continue on his crusade, orders him to take the ship back with the Enterprise to starbase 211-and informs Maxwell that he can command the ship back himself, or have it towed and be thrown in the brig.
Maxwell goes back to his ship, but before they reach Federation space, veers off. The Enterprise catches him just as he reaches another Cardassian ship, which he claims is the proof Picard needs, and he demands Picard board it. Picard refuses, but he is spared having to fire on Maxwell when O'Brien beams over and manages to convince Maxwell to give up. All is well-but before Gul Macet leaves the Enterprise, Picard tells him that Maxwell was right. (There are various pieces of evidence for this.) He tells Macet that he did not board the other vessel because he was there "to preserve the peace," but he tells Gul Macet to tell his leaders that "We'll be watching."