The Three Cities, Paris Volume V by Émile Zola

EVER since the execution of Salvat, Guillaume had become extremely taciturn. He seemed worried and absent-minded. He would work for hours at the manufacture of that dangerous powder of which he alone knew the formula, and the preparation of which was such a delicate matter that he would allow none to assist him. Then, at other times he would go off, and return tired out by some long solitary ramble. He remained very gentle at home, and strove to smile there. But whenever anybody spoke to him he started as if suddenly called back from dreamland.

Pierre imagined his brother had relied too much upon his powers of renunciation, and found the loss of Marie unbearable. Was it not some thought of her that haunted him now that the date fixed for the marriage drew nearer and nearer? One evening, therefore, Pierre ventured to speak out, again offering to leave the house and disappear.