The Devil is in the Details

Cass suddenly threw her head back, connecting sharply with the man's nose as she elbowed him in the ribs, slipping from the man's grasp momentarily to whirl around.
As she did so, her hand slipped to the knife, unholstering it and crouching low in a fighting stance.
"Lucky shot." The man spoke quietly, obviously trying not to alert the men in the other room, hands balled into fists.
"Certainly caught you by surprise," Cass growled, barely above a whisper. "Who are you, and why are you here?"
The man's head angled down, looking at the knife in her hand. His stance was as tense as hers, both prepared to spring into action should the other step out of line.
"You plan on using that?" the masked man asked.
Cassie's grip just tightened on the hilt of her knife. "If you take a step closer, you'll see. Now answer me. Who are you and why are you here?"
Mask's grin turned into a grimace and gestured to the cloth covering the top half of his face, obscuring his features somewhat.
"I don't really think you understand the point of a mask.''