Cleek: the Man of the Forty Faces by Thomas W. Hanshew

An ex-cracksman turned Scotland Yard detective, Cleek's slim and faultlessly dressed form is topped by an india-rubber-like face, of which he has remarkable control. With the power to distort and transform his visage and mimic any mannerism he desires, Cleek (with the assistance of his cockney assistant "Dollops") makes a super natural detective!