Hermione hadn't known there was a costume party at the Leaky Cauldron, but fortunately what she had on would do. She had attended a training in Advanced Socializing in Monte Carlo, and of course the Liaison had insisted that only full evening dress for herself and the rest of the Squad would do. And of course she was in semi-disguise to make it even harder to spot her.
That was why she wore a strapless midnight blue dress satin dress with a long slit up the side (carefully positioned so the wand sheath strapped to her thigh would not be noticeable). It was also why she'd charmed her hair into soft, loose red curls in a vaguely retro style, and given herself a temporary widow's peak. She didn't look like herself at first glance, and it had worked perfectly in the Casino (three Romanians who should have known her, and known her well, ogled the lovely redhead without a sign of recognition).