What does Maitre Hauchecorne pretend to be/do?
Maitre Hauchecorne finds a piece of string on the street. Being relatively poor and inclined to save things that might be useful, he picks up the string. However, he notes that he is spotted by his enemy, M. Malandain. Hauchecorne is embarrassed to be seen picking up something as small and trivial as a piece of string. So, he decides to at least give the appearance (to M. Malandain) that he is actually looking for something more valuable. He doesn't want Malandain to think that he is so poor and needy that finding a piece of string is like finding a small treasure.
Malandain uses this display to accuse Hauchecorne of having stolen M. Houlbreque's pocketbook containing five hundred francs. In his embarrassment and vanity, Hauchecorne made himself look like he was searching for a pocketbook or something valuable. Had he simply been humble, swallowed his pride, and acknowledged (to Malandain) that he did pick up a piece of string, the accusations might not have been made. Hauchecorne is innocent, but the townspeople have made up their minds that he is guilty. He spends the rest of his time trying to prove his innocence and this is perceived as being so defensive that is suggests guilt.