Read it through once

The last three sentences stung Tom into a fury, and he said to himself that if his father were only alive and in reach of assassination his mother would soon find that he had a very clear notion of the size of his indebtedness to that man, and was willing to pay it up in full, and would do it too, even at risk of his life; but he kept this thought to himself; that was safest in his mother's present state.