There's always a man. There's always a city. There's always an array of pseudo-scientific spells that combine with an arsenal of period handcannons to create open-ended, raw-knuckled firefights. And there's always a bit of an ending twist that knocks the entire premise off-rail, for good or for ill.
Burial at Sea's first episode eschews the lighthouse, at least - you begin in the office of an alternative-world Booker DeWitt who works as a private eye, right before he's given the case of his career by a classy dame with a Songbird necklace. In most respects, though, this is a straight and slightly dissappointing rehash of the Infinite plotline, that just happens to unfold on Rapture's stage.
Returning to Rapture, at least, is an undiluted pleasure. Set before the events of the original Bioshock, and equipped with Infinite's crowd-friendly engine, Burial at Sea gives you Andrew Ryan's aquatic metropolis at the height of its pomp and decadence. The trick to getting your money's worth is to linger over every inch - listen to every NPC conversation, study every billboard, watch every "In The Know" propaganda reel, drink in every art deco finishing.
There are some utterly spectacular bouts of fan service in store, from a theatrical close encounter with "troubled" artist Sanders Cohen, to a Bathysphere trip to the flooded malls of Fontaine Industries, entrenched hundreds of metres below the rest of the city. As an exercise in fleshing out the city's unruptured past, it's a huge success, engorged with acres of new art and dialogue. It's a sign of a world's staying power, when the sight of a remodelled Circus of Value vendor has you smiling and hugging yourself.
In terms of what you actually do, though, Burial at Sea is fairly tepid stuff - a fetch quest followed by shoot-outs that introduce Infinite's Tears and Skylines to Bioshock 1's Splicers and turrets, a puzzle that involves finding a new Plasmid, a puzzle that involves doing X of Y, and a boss encounter that's all about attrition.
There's scope for a little exploration, in order to recover equipment kits, audio diaries and the like, but the glee of discovery is deadened by the clumsiness with which Irrational wheels on that obligatory Shocking Revelation. It does, at least, pave the way for a much more intriguing Episode 2. Let's hope a change of protagonist is enough to rescue this expansion from the doldrums.
Burial at Sea hits Xbox Live tomorrow, 12th November. It'll cost you £11.99.
Rapture's worth another visit, but it also deserves better than this. One for serious fans only.