Flack is driving by three individuals in a car, and Terrence Davis, a police informant, gets in. They talk, and Flack tells Davis his time as an informant is over. Flack gets a call from Det. Angell, they talk about arranging dinner. Out of nowhere, a truck drives through the entrance of the restaurant where Angell is guarding Robert Dunbrook's son during a prison transfer. Flack hears this on the cell phone, along with the ensuing shootout, and he immediately rushes to the restaurant. He finds Angell on the ground, shot and bleeding badly. She is rushed to the hospital with Flack by her side.
Robert Dunbrook shows up, trying to get Mac's cooperation, but it doesn't come easy, given their previous history. His son was going to testify against him in court, so immediately he is a suspect with motive. During the investigation, Angell dies in the hospital. Mac gives a talk to the team (sans Flack) and other officers at the crime scene, and vows that when a member of the NYPD is killed, they will stop at nothing to find the killer. Adam places a GPS device on the bottom of Dunbrook's car, and is almost caught in the process. Eventually they track him to a warehouse, where he is overheard via the GPS device, negotiating with the kidnappers.
A gun is heard being cocked, and Mac, Danny and Flack (who are monitoring the device nearby), jump into action. They are shot at by a sniper who is on the roof using what appears to be an AK-47, and after a few minutes of trading rounds, finally get into the warehouse. Dunbrook is there, and the kidnappers drive off. "You just killed my son!" he says. Dunbrook now believes his son is dead, but Mac doesn't believe so, saying it would be foolish for the kidnappers to do so, and that would negate what their trying to accomplish in the first place. Dunbrook and Mac watch a video made by the kidnappers, showing Dunbrook's son reading a ransom note. Dunbrook believes the video doesn't help identify anything useful, but Mac knows otherwise.
At the end of the video, a kidnapper reaches to cover the lens and turn off the camera. Mac and Hawkes are able to freeze the video while he does so, and a shot of one of his fingertips is enhanced to make out a print. They run it though the system, and are able to make a match in the system. A suspect is found. The team finds the Humvee, and find a round stuck in the window. Mac noted it should have penetrated the window, and shortly the team finds the Humvee is bulletproof, even the tires. The driver left blood on the seat, and a hair on the gas pedal, which Hawkes later determines is from a bat.
Terrence and Flack cross paths again in the streets, and Terrence hands Flack a newspaper on which he wrote information that leads the team to a customizing garage. It was there the humvee was given the "presidential treatment". The individual they question recognizes the suspect in the picture shown to him as one of the occupants of the Humvee that was brought to him. Eventually they track down the suspects hideout, and enter with force. A shootout ensues between the team, SWAT and the suspects. Dunbrook's son is found and is brought out of the building. Flack finds a suspect laying on the ground downstairs. He has a wounded shoulder from his earlier shootout with Angell, and is carrying the same Desert Eagle used to kill her. Flack quickly puts the pieces together and executes him.
Back at Headquarters, the team has headed out for drinks after a long day. Stella and Mac exchange conversation and a friendly hug. Stella then asks if he is going out to "the bar" with the team, to which he says that he'll be along shortly. Mr Dunbrook appears, giving Mac a newspaper with Angell's picture, and a headline honoring her. Mr Dunbrook says that even though his son is going to testify against him, he still loves him. On the way out, he tells Mac to "be safe"--which could be either a kind gesture or a veiled threat.
The team is in a bar, having drinks. Mac shows up just as a toast is about to be made to honor Angell. A car comes slowly around the front and rolls down its side windows, from where an automatic weapon appears. The gunman inside the car fires against the team inside the bar, and sends them ducking for cover.