A family riding in a car pulls up to a building when the father gets out of the vehicle. His wife and son stay in the car. He approaches an apartment with a bag of groceries and shoots through the front door.
Entering the apartment he cannot find the man he shot at and hears a commotion out the window. The man he shot went through the window and landed on his car, left curbside on the street.
3 months later, U.S. Marshal Mary Shannon and her partner go to a train station to pick up a witness. Tasha Turischeva is entering the Witness Protection program, and Mary, along with her partner Marshal Marshall Mann, have to transport Tasha to her new apartment. Mary has already decided it will be a bad day. It is her birthday.
Mary's boyfriend Raphael, is sent to pick up Mary's sister Brandi who has arrived in town for the "surprise" birthday party. Brandi is annoyed that Mary is not the one to pick her up and yells at Mary, who tells her to start walking. Raphael takes Brandi home by way of the youth center where he leaves her outside with local youth gangbangers to try and intimidate her. Brandi steals his vehicle.
Mary gets a call that two bodies were found, and one might be Frankie Jr., son of her witness Frankie Santoro, Sr. Mary goes to the crime scene, taking Tasha with her. Mary and Marshall take Tasha to her new apartment afterward, and Mary promises to bring her groceries later.
Mary comes home to find Raphael and Brandi arguing over Brandi's theft of his vehicle. Mary's mother, Jinx, is calmly sitting in a lounge chair drinking during the argument. Raphael turns the argument around on Mary, blaming her for Brandi's leaving him stranded.
Mary's family are not aware of her job so they don't comprehend the stress she is under. Mary has to find out if Frankie, Jr. was murdered because of his father or if he and the girl murdered with him were due to another cause.
Mary solves the murder and heads for home to end her horrible birthday. She remembers Tasha and finally brings the girl groceries at 3:00 am.