How far did their knowledge of the latter go?
They must be ignorant of the part played by Salvat.

It was surely impossible for them to piece together all the unforeseen circumstances which had brought about their father's meeting with the workman, and then the crime.

Mere-Grand, no doubt, was in certain respects better informed than the others.

But they, the sons and Marie, neither knew nor sought to know anything.

And thus what a wealth of respect and affection there was in their unshakable confidence in the father, in the tranquillity they displayed directly he sent them word that they were not to be anxious about him! "Madame," Pierre resumed, "Guillaume told me to give you this little key, and to remind you to do what he charged you to do, if any misfortune should befall him." She started, but so slightly that it was scarcely perceptible; and taking the key she answered as if some ordinary wish on the part of a sick person were alone in question.