you have to help the elder or find a wallet and give it to its owner to unlock miller’s quest. If you wanna help with that, you can pm me on Patreon (if you’re my Patron) or on Discord ;)
Thanks, this explains it. I have poisoned the elder's son and took the money from the wallet. I will try doing something differently on my next playthrough after the update (I am curious about the contents of the chest in the elder's house, so I definitely need to try saving his son).