Even when he wrote the letter to the prison, promising to meet Ida, he had acted as if out of mere humanity.

It needed a chance such as the present to open his eyes.
That she should quit the prison, and, not finding him, wander away in blank misery and hopelessness, most likely embittered by the thought that he had carelessly neglected to meet her, and so driven to despair--such a possibility was intolerable.

The fear of it began to goad him in flesh and spirit.

With a sudden violent stringing of all his sinews, he wrenched at the bonds, but only with the effect of exhausting himself and making the walls and ceiling reel before his eyes.

The attempt to utter cries resulted in nothing but muffled moaning.