|“||Promise me she'll be okay, Morgan.||”|
— Spicer's last words
Born in Santa Monica, California, Matt had a regular childhood with his parents, Joe and Sylvia, and baby sister, Kristin, until July 28, 1984, when a serial killer who later became known as The Prince of Darkness (later identified as Billy Flynn) broke into their house. He woke Matt up, placed him and Kristin in the closet of their parents' bedroom, raped Sylvia in front of their eyes, killed Joe, and then her. Matt and Kristin were placed in the care of their grandparents and told that their parents had died in a car accident. Kristin was too young to remember the incident and Matt, who witnessed everything, chose to believe this, repressing the truth. He later became a police detective for the Los Angeles Police Department and specialized in robbery and homicide crimes, of which was likely subconsciously spurred by his parents' murders. At one point, he was married, but they eventually divorced, presumably due to the strain of her being married to a police detective. He had a daughter, Ellie, with her and gained custody of her because the mother frequently traveled in the line of work.
Our Darkest Hour (Part 1)
When Billy returns to California after travelling all around the U.S. for 26 years worth of killing, Matt investigates the crimes together with the BAU. During the investigation, he is mostly partnered with Morgan, with whom he initially clashes with when they have conflicting views over interrogation tactics with a survivor. When Garcia produces a complete list of Billy's crimes over the years, the truth about the Spicers' deaths is revealed to him. The two then deduce that Billy is partially recreating his original California murders in order to taunt Matt and that he will go after Matt's family: Ellie and Kristin. Matt and Morgan drive to their home and find that Billy has already abducted them. Morgan figures that he will take them to Matt and Kristin's parents' old house. Upon arriving, Billy incapacitates and ties up Morgan and Kristin before forcing Matt to get on his knees and drop his gun by holding Ellie hostage. After Matt recognizes the impact Billy has on his life, he makes Morgan promise to keep Ellie and Kristin safe. Billy then shoots Matt in the chest at point-blank range, execution style, and leaves, taking Ellie with him despite Morgan and Kristin's protests.
The Longest Night (Part 2)
Matt did not survive the gunshot, and his death took a toll on Morgan's emotions. However, his death was not in vain: Ellie was released by Billy, who in turn was shot dead by Morgan when he took a couple hostage in their house. Unfortunately, Kristin, who was left badly wounded after being assaulted by Billy, died from her injuries.