Head of a Woman in Jerusalem - Tanner

Head of a Woman in Jerusalem 
Henry Ossawa Tanner, 20th century
At the Smithsonian American Art Museum, Washington DC

Quite striking because the picture keeps leading you back to her face, which has me wondering what she's looking at -- is it hesitation? Interest? She seems to be concerned about something, and the touch of blue on her shoulder keeps catching my eyes as well.