Little is known about Barton's personal life, other than he worked as a trauma surgeon in Washington, D.C., and his wife died when their son Jeffrey was ten years old from breast cancer. On January 3, 2009, he operated on a middle-aged Hispanic man who survived a car crash, while an eighteen-year-old named Jason Meyers suffered brain damage. Barton decided to not try operating on Jason due to the severity of the brain damage and the fact that it was too late to save him. He was confronted by Jason's father Patrick, who demanded to know his son's condition and became angry when Barton initially didn't remember Jason's name, needing a nurse to show him his file. On May 18 of the same year, Jason, who had been kept on life support, was disconnected and declared legally dead. The day afterward, Barton received a letter written anonymously by Patrick (who signed it as LC) declaring that he would kill Jeffrey. To protect his son, Barton kept him inside the family home, telling him that there was a threat against him at the hospital. During the following two days, two middle-aged Hispanic men were murdered by Patrick, eventually leading to the summoning of the BAU, sans Hotch, who at the time had just undergone a stabbing attack on him and was intentionally taken to a hospital by his assailant.
In the episode, the BAU investigate Patrick's killing spree and are led to Barton by Detective Walker. They interrogate the doctor, who informs them of the measures he enacted to protect Jeffrey. Jeffrey eavesdrops on the conversation, sneaks out of the home, and goes to school in order to protect himself and his father and to prevent someone else from getting killed. When he calls Barton to inform him of what he had done, Rossi, Morgan, and JJ rush to the school, while Reid and Prentiss stay behind with Barton at the home to investigate his most recent case-files and narrow them down as thoroughly as possible. Using the information from the letter, Reid and Prentiss give a profile of the unsub to Barton. As time passes and Jeffrey is closer to being released from school for the day, he becomes increasingly distressed, especially when Prentiss is forced to leave to find Hotch, leaving him alone with Reid.
After they are unable to find anything of importance in the files, Reid decides to identify who the unsub may be through the words that were written in the letter. After going through the letter again, Barton remembers Patrick's confrontation with him. With that information, they identify Patrick as the unsub. Later, Barton goes out of the house to pick up Jeffrey, just as Reid realizes from a phone call with Prentiss the meaning of LC (a hospital administrative term standing for "Living Children" referring to patients going on life support without an order to not resuscitate). Realizing that Patrick plans on killing Barton instead, Reid rushes out of the house, just as the doctor is being confronted by an armed Patrick, who fires a shot that hits Reid's leg. Reid has Tom grab his revolver which he dropped after getting shot and takes cover behind Reid and, after attempting to talk Patrick down, shoots him in the stomach when he attempts suicide by cop. However, Patrick survives and is successfully treated by Barton as paramedics arrive, to which he then reunites with Jeffrey.