Like Father, Unlike Son: His father Josef was a quiet, nonconfrontational man who preferred quiet burglaries. Karl, on the other hand, is more confrontational and enjoys the adrenaline rush he gets from his career. Its mentioned in Territorial that when he was younger, Karl occasionally found himself thinking that Josef was a coward.
Older Than They Look: He looks to be somewhere in his mid-thirties, but is actually fifty years old. Justified because hes a werewolf. Other werewolves take to calling him old man, to the confusion of anyone who doesnt know how old he actually is.
Will They or Won't They?: He and Hope initially have an on-again, off-again relationship, mostly because of Karls confidence issues. He finally proposes to her in Lucifers Daughter.
Working with the Ex: He returns from Europe (after apparently leaving for good) to honor his half of a debt he and Hope owe to Benico Cortez in Personal Demon. Over the course of the novel, he reconciles with Hope and they (eventually) get back together.