|“||What's my name? My name's Francis Goehring.||”|
Frost's alcoholic, abusive father threw him out when he was 15. After that, his life became a series of jails and institutions. At some point, he took a job at a flower shop in Great Falls, Montana as a clerk and met Francis Goehring, a sadistic serial killer whom he served and actually developed secret romantic feelings for. He helped him abduct local women for him to torture. Frost would videotape him doing this and also clean his cottage, bury his deceased victims, and tend the roses planted on their graves.
After Goehring's suicide in the beginning of the episode, Frost, who had become totally dependent of him, suffers a massive identity crisis, kills Angela Miller, the last woman he and Goehring had abducted, destroys all pictures of his past and the torture videos of Goehring's victims, and changes his appearance to become the spitting image of Goehring, even going so far as to cut his face to recreate his scar. He then abducts a woman named Becky from a gas station, the act being witnessed by the cashier, and takes her to a cliff with the intent to torture her, but isn't able to derive any true satisfaction. The BAU quickly track him down, having deduced him to be Goehring's partner, and Hotch tries to negotiate with him. The local police deputize Harris Townsend, a local militia leader and former sniper, to kill him if they aren't able to talk him down.
Frost refuses to surrender, pushes Becky aside, raises his assault rifle, and aims at Hotch. He is consequently shot in the back by Townsend, the bullet severing his spine and cutting into his main artery, killing him instantly.
When he helped Goehring abduct his victims, Frost forced them into their car and took them to the cottage. He would then pick Goehring up from wherever he disposed of his victims' cars. He would also record him torturing, raping, and presumably killing his victims with a handheld camera. After Goehring killed his victims, Frost would bury the bodies on the cottage and plant roses over the graves.
Since Frost only killed one person during his crimes without Goehring, the term "M.O." may be misused. He killed Angela Miller simply by shooting her twice in the upper torso with a Smith and Wesson 13 revolver. When he abducted Becky, he took her to a cliff in Black Eagle Peak (presumably because he realized the BAU and local police found the cottage), tried to recreate Goehring's style of torture (but didn't succeed since he wasn't a sexual sadist like Goehring), and held her hostage with an M4A1, which he attempted to shoot Hotch and Townshed with.
- September 2006: Michelle Lawford (abducted by both and killed by Goehring)
- May: Jennifer Hillbridge (abducted by both and killed by Goehring)
- September: Darcy Cranwell (abducted by both and killed by Goehring)
- November 5: Angela Miller (was abducted by Frost and Goehring together; shot twice in the upper torso by him after Goehring's death the next day)
- November 7:
- Becky (abducted, attempted to torture, and intended to kill; was rescued)
- Aaron Hotchner (attempted to shoot)