Read it through once

By degrees he was inclined to believe that she had faintly attempted, at least, what she said she had done; and his horror at her impulse was mixed with amazement at the strength of her affection for himself, and at the strangeness of its quality, which had apparently extinguished her moral sense altogether. Unable to realize the gravity of her conduct, she seemed at last content; and he looked at her as she lay upon his shoulder, weeping with happiness, and wondered what obscure strain in the d’Urberville blood had led to this aberration—if it were an aberration. There momentarily flashed through his mind that the family tradition of the coach and murder might have arisen because the d’Urbervilles had been known to do these things. As well as his confused and excited ideas could reason, he supposed that in the moment of mad grief of which she spoke, her mind had lost its balance, and plunged her into this abyss.