Read it through once

Beaufort, though clearly annoyed at finding him with Madame Olenska, had, as usual, carried off the situation high-handedly. His way of ignoring people whose presence inconvenienced him actually gave them, if they were sensitive to it, a feeling of invisibility, of nonexistence. Archer, as the three strolled back through the park, was aware of this odd sense of disembodiment; and humbling as it was to his vanity it gave him the ghostly advantage of observing unobserved.