Derek was apparently held captive in a remote cabin by a torturer-for-hire named Edgar Solomon, played by Charles Mesure, and his team of goons. It was not clear who hired Edgar and his team to abduct and torture Derek.
As Edgar tortures Derek, a trail of white phosphorous smudged down his torso. It seems to be like a chemical of some sort. It was then that the BAU agent started hallucinating first about having an idyllic home life with Savannah and their two future kids.
But as he begins to feel more pain, his fantasy of a family life was changed by the memories of his late father Hank Morgan, played by veteran actor Danny Glover.
Hank served as a guide for Derek during his ordeal and offered two options for him – either to die easier or hang on and bring his torturers to justice.
Then another flashback scene popped up to his mind back when he was only 10 years old, the very same day that his policeman father was fatally gunned down while trying to stop a purse snatcher. Then there was also a flashback of him at the age of 15 when he was abused by a pedophile.