The tough outlaw 'Sierra' Bill falls in love with the traveling girl violinist Nelly Gray. Sierra forces her into marrying him. They have a child, but family life is interrupted by the gambler Ringe, who not only persuades Nelly to leave her husband but ruins Sierra at the gaming table. With thoughts of vengeance, the angry Sierra breaks out of jail and goes after Ringe.
Unfortunately the movie The Testing Block is not yet available on HBO Max.
| Editing | LeRoy Stone | Editor |
| Writing | William S. Hart | Screenplay |
| Writing | William S. Hart | Story |
| Writing | Lambert Hillyer | Scenario Writer |
| Art | J.C. Hoffner | Art Direction |
| Writing | Lambert Hillyer | Screenplay |
| Directing | Lambert Hillyer | Director |
| Camera | Joseph H. August | Director of Photography |
