eyebrows

Bernard is mystified as to why everyone he encounters reacts strangely towards him, but he soon realizes that his facial expressions, more specifically his eyebrows, are conveying emotions he does not feel, leaving Bernard to wonder if he is doomed to live a life with horrendous brows.

"Cat detective Inspector Brunswick and Nelson, his assistant, investigate when they discover that an admiral depicted in a prized portrait is missing an eyebrow"--OCLC.