A town called “Illmarsh”, with strange, sullen villagers with strangely fish-like features? Rumors of forbidden cults? Miles and miles of rocky, forbidding shoreline? Yes, it’s “Paizo does Lovecraft” time again, with Greg A. Vaughan’s Wake of the Watcher (part 4 of 6 in the Carrion Crown adventure path). Not that Paizo is a stranger to Cthulhu, numerous old modules have had direct Cthulhu references, but this is perhaps the most direct Cthulhu scenario to come from them to date. On the other hand, it is Pathfinder and the end result is less the nameless dread Lovecraft was going for and more “Strange, squamous shadows advancing towards us? I fireball them!”.
The plot has the PCs chase the evil cultists to the aforementioned town of Illmarsh, where the tracks grow cold (and damp). The villagers are… strange, and getting clues may require the PCs to venture into places the townspeople would rather they not venture in. There are a few nice red herrings here to throw seasoned Cthulhu players a tiny bit off track, but generally players familiar with their Lovecraft will pretty much get what they expect. That’s not necessarily a bad thing; as noted, the combo of D&D and Lovecraft does bring a distinctly different tone to the proceedings, and not everyone is all that familiar with Lovecraft in the first place.
It’s a fairly nice continuation of the Carrion Crown storyline, though I have more and more trouble figuring out just why the PCs would track the cultists in this case. Why not just go home and find something easier and more productive to do? I suspect many GMs will need to add some carrots (or sticks) of their own here, to bring some urgency and sense of motivation to the proceedings. The story here is quite removed from the earlier plot, and this installment could easily be run as a standalone adventure without much extra work. For a GM looking for a slightly unusual tone for a D&D adventure, this might well fit the bill.