A set of burning eyes are fixed upon the collie's every footfall, unblinking and full of ancient, endless longing. The Phantom knows this place near as well as he knows every passage, every stairwell, every hidden nook and rafter and trapdoor of the old Opera House, and so no thoughts go into his own silent tread... his feet know the way. His ears twitch at the sound of the sharply closing gate, but he doesn't otherwise startle. The black shepherd's mind is too full.
Merging with the world's growing darkness, the Phantom stalks the object of his desires.
(Only just discovered this, and was Overwhelmingly Compelled to reply.)