Read the passage and answer the question that follows.
Ah! Whatever could be said was said. All held him guilty. Even his own mother who claimed to understand him the best. All had betrayed him in his hour of need. Yet, there he was, still with a sparkling hope and knew that the truth must prevail. In the cold, dark and damp cell he never for a moment lost faith in God and goodness and was waiting anxiously for an angel to come, plead non-guilty for him and free him of his miseries.
The truth must prevail means?