When the flashback kicked in I groaned because I was sure this was just a retread of Study in Scarlet. Oh, a secret society in America is blackmailing a man who later commits murder? And there's a damsel in distress in the middle of it? 
 The similarities were quickly forgiven by the engrossing drama, and eventually deftly subverted as well. Melodramatic certainly but I can't help it o love the stuff.