It was at this moment that I chanced to glance at Holmes and saw a most singular intentness in his expression. His face was as set as if it had been carved out of old ivory, and his eyes, which had glanced for a moment at father and child, were now fixed with eager curiosity upon something at the other side of the room. Following his gaze I could only guess that he was looking out through the window at the melancholy, dripping garden. It is true that a shutter had half closed outside and obstructed the view, but none the less it was certainly at the window that Holmes was fixing his concentrated attention. Then he smiled, and his eyes came back to the baby. On its chubby neck there was this small puckered mark. Without speaking, Holmes examined it with care. Finally he shook one of the dimpled fists which waved in front of him.