Dumbledore Senses Lord Voldemort's Magic in the Cave
Pages 557-558
Upon emerging from the water, Harry and Dumbledore enter the cold, dark cave. Dumbledore, using his wand and his magical intuition, senses that Lord Voldemort's magic has left its traces in the cave. He deduces that they are in the outer chamber and that they must penetrate further to reach the Horcrux.
