The Phantom City (Doc Savage #10)

They capture him, and for some reason want a submarine. He takes them to the Hidalgo trading company and gets the drop on them there, knowing the layout. In the dark, he also kayoes Monk, and they come across a stunning, seemingly mute, shockingly white-haired woman.
Said beauty is scared to bits by Monk, who she thinks is a 'White Beast' ape monster!

To produce a fast interrogation, they try trickery, scamming the assassins with a mythological figure telling them to spill the beans