The fog of Far Harbor is to be feared. It inflicts radiation poisoning on those who dare to trek through it, it gives birth to horribly slimy creatures of the deep, and it does an admirable job of obscuring your view of the fiends that stalk the wilderness. The island's residents have a right to fear the mist: it keeps them penned inside of their small settlements, forced to await the next inevitable mutant attack – but you'll come to loathe the fog for entirely different reasons.

Far Harbor is Fallout 4's first "proper" expansion; it's set on a whole new landmass that lies North of the Commonwealth – a treacherous island that's crammed with new quests and secrets. Initially, you're sent there to do a touch of detective work and find a missing person, but, unsurprisingly, it isn't long before you're pulled into the growing conflict between the isle's three main factions.

Right from the start, it's clear that Bethesda has listened to criticisms regarding the main game's writing. Almost as soon as you step off your boat, you're swamped with dialogue choices and the rants of disgruntled settlers. The developer tries far harder to spin subplots here that bubble away beneath the add-on's overarching story, and the result is a slice of content that, narratively, feels a little more refined than Fallout 4.

Aside from a few tediously predictable characters, Far Harbor's cast isn't too shabby, and although the quality of the dialogue still doesn't come close to matching the best that the genre has to offer, there's enough player choice here to keep you invested. What's more, your actions have a direct impact on the conclusion of this 20-or-so hour adventure, allowing you to leave your mark on the creepy island's history.

However, despite its best efforts at crafting a complex story, Far Harbor stumbles when it decides to roll out a series of poorly judged quests around the plot's halfway point. Without spoiling anything, one of these tasks sees you fiddle with the game's crafting system as you solve puzzles. While this segment certainly offers something new, it feels bafflingly out of place and drags on for far too long. Just when the story's kicking into gear and you're faced with some tough choices, you're wrenched from proceedings and forced to endure this clumsy attempt at puzzle-solving gameplay. It's maddening.

Fortunately, the good outweighs the bad when it comes to the rest of the quests that are dotted around the island. Generally speaking, most of these are your usual Fallout 4 affairs – go to an area, kill the enemies – but the new setting and fresh batch of foes do a fine job of keeping things interesting. Naturally, there's effective new equipment to find, too, and there are some brilliantly designed, intricate locations that play host to several superb combat scenarios. Indeed, Bethesda's prowess at creating environments that beg to be explored and looted is once again a key selling point in this expansion.

Or at least, it would be, if Far Harbor didn't run like a salty sack of shite on PlayStation 4. Approaching or walking through the aforementioned fog that covers most of the island murders the framerate on Sony's console, crippling any sense of adventure as you scavenge your way across the impressively detailed setting.

At times, it's worryingly easy to look past the inherent bugginess of Bethesda's titles; Fallout 4's rewarding gameplay loop makes it difficult to put down even though you know that the game should run better than it does. But in Far Harbor's case, Bethesda's released a product that comes dangerously close to being a chore to play, and that's just not good enough.

Conclusion

Far Harbor should have be an easy sell to those who have picked the Commonwealth clean, but something terrible lurks within the fog. Serious framerate issues on PS4 make the expansion stink like the rot of a mutated fishman, killing any sense of adventure in what is otherwise an intruiging add-on. If the problem's patched, feel free to add a few points to this review's score – but until then, you should steer your ship clear of Far Harbor's foreboding coast.