Rebecca Bryant (née Garner) was an incidental character who first appeared in The Fisher King, Part 1.
Background
Rebecca was born on July 15, 1988, in Las Vegas. She lost most of her family in an house fire that occurred on the night of October 12, 1992, caused by faulty wiring. Her father, future budding serial killer Randall Garner, saved her and suffered severe burns when trying to save the others. Rebecca was found crying in her backyard, apparently unharmed. Her father spent nearly three years in a burn ICU and decided to give up parental rights on Rebecca during his time in the hospital. She was first taken in by Joseph and Celia Bryant as a foster child before being formally adopted by them on December 4, 1993 in Clark County, Nevada. Upon maturing, Rebecca acted out severely, running away five or six times, doing drugs and committing vandalism, theft and truancy. When she was abducted from South Boston, Virginia on February 25, 2004, by a now-delusional Randall, nobody bothered to make a full search because of her rap sheet. She was held captive in a tiny room in his basement, chained, for over two years.
On Criminal Minds
Rebecca's disappearance is finally brought to the attention of the BAU by Randall himself. He challenges the BAU into finding her with a series of cryptic clues and riddles. The BAU contacts Rebecca's adoptive mother, who revealed portions of her troubled past. Rebecca is not shown much in this episode, only for a few minutes and in a video. In this episode, Garcia finds out more about Rebecca's past and her father. Reid brings in his mother, Diana, who is residing at the same sanatorium as Garner did. She knew him and also knew about Rebecca. The BAU travel to his house where they find him, tied to a bomb. He detonates it, attempting kill himself and Reid, but Reid is able to escape. The team finds Rebecca in Garner's basement and saves her. About one year later, Rebecca is contacted by a man posing as Jason Gideon, claiming to be following up with past victims. The man is actually serial killer Frank Breitkopf. Rebecca becomes suspicious when Frank begins discussing the psychology of rape victims, even though she was never raped. A phone call comes from Hotch to warn her, but it is too late. While still speaking to Hotch, Rebecca is tranquilized by Frank, who then brutally murders her.