3 AM is the first episode of the first season of the television series The Punisher.
Former Marine Frank Castle takes the law into his own hands while struggling to come to terms with his traumatic past.
In rural Alabama, the Punisher chases down two members of the Dogs of Hell, forcing them off their motorcycles and then running them over with his truck. In Juárez, the last member of the Mexican Cartel arrives home to a hero's welcome. Across the border in El Paso, Texas, the Punisher kills him with a single round from a sniper rifle. At JFK International Airport, the last survivor of the Kitchen Irish, Mickey O'Hare tries to flee to Dublin, Ireland. The Punisher tracks him down and strangles him with his own tie. With his family avenged, the Punisher burns the vest he spray-painted the skull onto.
Six months later, Castle is working construction in New York City under the name of "Pete Castiglione." Keeping to himself and working his anger out by destroying walls with a sledgehammer, he is hassled by other workers led by Lance who thinks he is not all there. Lance also hates the fact that Castle's constant work from early to late is making them all look bad and resulting in less overtime. Castle does not rise to the bait, even when they knock over his lunch pail and tread on his sandwich. The new guy on the crew, Donny Chavez, tries to befriend Castle, but is kept at arm's length.
At a veterans support group, Curtis Hoyle helps other veterans through their trauma, including Lewis Wilson, O'Connor, and Isaac Lange. Castle listens outside. Once the group leaves, he talks to Hoyle, who is an old friend from his days in Afghanistan. Hoyle encourages Castle to let the Punisher stay dead since the whole world believes it anyway.
At the New York office of United States Department of Homeland Security, Agent Dinah Madani meets her new partner, Agent Sam Stein. She is annoyed that she was transferred from Kandahar to stop her looking into the murder of Ahmad Zubair, a local police officer. Although discouraged from investigating the murder, Madani asks Stein to get her all the information they have on Colonel Ray Schoonover and Frank Castle.
Chavez tries to ingratiate himself with Lance and his friends by offering to buy the first round at a local bar. However, he gets stuck with the whole bill. During the night, Lance tells Paulie that he needs to do another job since he is in debt to a loan shark from the Gnucci Crime Family. The next day at the construction site, Paulie tells Lance that they can hit a high-stakes card game run by the Gnucci's, figuring that Lance would love to pay the loanshark off with their own money. Scut is injured on the job, forcing Lance and Paulie to recruit Chavez to help them out. Castle overhears everything but does not involve himself, even ignoring Scut's accident.
Madani meets with her mother, Farah Madani. Over a glass of wine, they have a frank conversation about what Madani hopes to achieve.
Castle tries to read in his apartment, but flashbacks and visions of his wife's murder compel him to return to the construction site and continue working. Lance, Paulie, Chavez, and Leo rob the Gnucci card game, but during the heist Chavez drops his wallet revealing his ID for all to see. Fleeing the scene, Lance decides to kill Chavez so he does not rat them out once the Gnuccis catch up with them.
They beat him up and throw him in a hole being filled with cement. Seeing the commotion, Castle uses the sledgehammer to kill Lance, Paulie, and Leo but not before Lance reveals the location of the card game. Castle throws a rope down to Chavez who hauls himself out of the cement to find the bag of money tied to the end with the words "Leave Town" written on it in blood.
Castle heads to the Linello's where Tony Gnucci is preparing to go after Chavez, starting at his grandmother's house. Castle kills them all. As he leaves, someone watches him on surveillance cameras, identifying him by "gait recognition mode."