Final answer:
The accurate translation of the excerpt is "the thief and his people," and "They opened the door." This maintains the original subject plurality and perspective.
Step-by-step explanation:
The best translation of the dialect in the excerpt is "the thief and his people," came the cool reply. "They opened the door." This translation maintains the original meaning without changing the number or perspective of the subjects involved. It is consistent with the third person narrative perspective and accurately conveys the action taken by multiple people associated with the thief.