The Dummy (1929)

"LISTEN-to this 100% Talking Comedy Farce There's a volley of snappy humor when you hear the Dummy talk. A STAGE PLAY ON THE SCREEN"

The title character is office-boy Barney. Pretending to be a deaf-mute, Barney tries to trump his detective boss Walter Babbing by tracking down the person who kidnapped Peggy Meredith, the daughter of wealthy Agnes and Trumbull Meredith.