Complex sentence: Unfortunately for Claire, Randall has earned the "Black" in spades and detains her, asking why she is travelling alone in a "state of undress" and concludes that she is a prostitute.
Split into simpler sentences: Unfortunately for Claire, Randall has earned the sobriquet "Black" in spades. Detaining her, he asks her why she is traveling alone in a "state of undress", and concludes that she is a prostitute.