At first, he hadn't heard her voice and had barely even registered the sound of the lock being broken off the door to his cell; he was so lost in his own world. Something, however, beckoned him to open his eyes--the were now brown, plain and dull--and peer out the empty space before him. Only the space wasn't empty.
He expected the professor, the madman who'd ran tests on him and tried to torture him into bending. That wasn't who Zuko saw, however. And for a moment, he simply stared and blinked, a million emotions filtering across his face--confusion, disbelief, hurt, sorrow, anger (if he could've bent, he would be spitting flames in frustration)...
The prince found his footing and stood stepping out cautiously towards the pair, though he addressed the one who spoke to him.