The Collector 2x13

"Beginnings" juxtaposes two stories: the Devil's initial training of Morgan as the first collector, and Morgan's memories of the beginning of his 10 years with Katrina. In the course of the episode we see the origin of the memories, both tender and troubling, that maintain Morgan's humanity even after Katrina's death, and also the Devil's nearly-successful first strike in snuffing out that humanity completely.