Twin Oaks is a tiny, sleepy little thorp located just within the sheltering eaves of a great forest... so of course something is going to go wrong, something will disturb their peaceful life, and indeed it does. The background for the DM describes just what it is, but as the main antagonist is desperate to avoid notice new arrivals in the settlement do not.
By its very nature, this is a good adventure to drop on the party as they are travelling about their own business. All you need is a suitable small village on the edge of a big forest. On the other hand, if you prefer you may want to use the main antagonist as a recurring figure in an ongoing campaign. Up to you. The hooks supplied cater for both eventualities: pick the one most appropriate to your needs and your players.
There are descriptions of the settlement and the surrounding forest, with maps originally published in the Map-a-Week series on the Wizards of the Coast website (the links still work as of the time of writing, but the versions included in the adventure are just as good). There are notes about what the antagonist is up to, as well as his full statistics for when he is discovered, whilst the house-by-house notes for the settlement provide subtle clues that all is not as it should be, hopefully prompting the party to investigate further. They are quite subtle and you might want to play them up a bit to ensure that the party actually takes notice.
A nice feature is that the antagonist is powerful enough that he might well be able to escape from a party of the suggested level, to remain a thorn in their sides for some time thereafter even if this is their first encounter with him. However, given his nature, there are no options for negotiation - most parties will be eager to destroy him once they realise what is going on...
[5 of 5 Stars!]