BioShock isn't an easy game to follow. A meticulously detailed and hugely distinctive gameworld, a remarkable story with a show-stopping twist, and two completely different endings - one of them apocalyptic — doesn’t leave a lot of room for tentative updates.

2K Marin has solved one issue simply by sticking with the original’s failed underwater utopia of Rapture as its setting. In doing so, it ties off the timeline: BioShock 2 takes place after the first game, but it doesn’t commit to what’s happening on the surface. The story, the studio’s keeping very close to its chest. But the basic setup is a whopper: you aren’t a hapless interloper, you’re a Big Daddy. And you’ve just been knocked off the top of the food chain. Years after the Little Sisters left Rapture, one has grown up and come back.

“People have talked a lot about prequel or sequel,” says creative director Jordan Thomas. “If we did a pure one of either of those, we wouldn’t be surprising you enough.” Instead, BioShock 2 is set “10 years–ish” after the first game in a battered but still largely intact Rapture.

“We didn’t think BioShock would be BioShock without Rapture,” explains lead artist Hogarth De La Plante. “Rapture was a really fascinating place, and there were lots of compelling untold stories and unexplored locations still within the city and within the mythology.”

The ending of the first game is never stated, although it’s become the stuff of legend among the once-human Splicers still fighting for dwindling reserves of genetic-upgrade material Adam. This vague stability is disturbed by the Big Sister: one of the original Little Sisters who has grown up, returned, and equipped herself with a sort of sports edition of the Big Daddy suit. For reasons 2K won’t reveal (and hey, letting the game reveal its own story is a large part of the fun), she wants to bring back the old Rapture, and is abducting girls from the surface to turn into Little Sisters. The city is hers now, and she guards it closely.

Join The Family

This is spelled out in the first minutes of our demo, dubbed “Hunting the Big Sister,” as we gradually awake to the radio nagging of one of Rapture’s few survivors — Dr. Tenenbaum. Older, more tired, and still just as guiltstricken, she’s your advisor as you take your first tottering steps.

And they’re big steps, because you’re an integral part of Rapture. You’re no normal Big Daddy — you’re the very first. The prototype, left in a puddle somewhere in the back of Dr. Suchong’s lab, capable of much more than your dimmer successors. You’re leaner, faster, and can use Plasmids as well as the monstrous mining tools equipped as standard. Both can be upgraded as in the original game, although the Plasmid system is more gratifying. Every upgrade you make gives a new Plasmid ability; so updating Incinerate, for instance, takes you from launching fireballs to wielding a built-in flamethrower.

You’re more than capable of taking down other Big Daddies (though once again, they’re no pushovers), which begs the question: Why? Another secret, we’re told. “As the prototype, you’re part of Rapture’s history. A lot of things make you special,” explains Thomas. “Suffice to say, they decided to simplify. I can’t really tell you about the incidents that lead to that…”

Regardless, you’re still one of the toughest things in Rapture, as the demo shows by dropping the player into a group of normal, short-lived Splicers. BioShock players will recognize the sudden rush with drill outstretched, and see that it’s much more satisfying from this side of the diving helmet — luckless Splicers just expire in a screeching, blood-splattering explosion like a pre-dentist nightmare. Another is quickly flamegrilled; turning to the third, a mere gesture with the drill makes him turn and run.

“The Splicers fleeing from you is something that actually can occur when they get pared down enough,” says Thomas. “It’s an important part of the fantasy of being a Big Daddy.”

A less obvious plus is the ability to go outside Rapture, as you can now survive underwater. You can use this to sneak peeks into internal areas (some recognizable from the first game) and harvest Adam-carrying slugs straight from the seabed, but it’s also the best way to take a break and just marvel at the wonderland you’re playing in. This is the money shot of the demo, trudging through the plant life and marine debris while the sea rumbles and roars around you, the stunning structures of Rapture rising overhead. It’s breathtaking.

Let's Adopt

But the most important part of being a Big Daddy is, of course, your relationship with the Little Sisters. As with the first game, how you deal with them affects your progress — but this time you’re fighting with, rather than against, them. Having dispatched the first group of Splicers, we go on to rescue a lone Little Sister from Splicers that had slain her protector; in the game it’ll be you doing the slaying and then slotting in as the new, slightly blood-streaked father-figure afterward. Little Sisters are so strongly conditioned that they can overlook this, and will willingly hop on your shoulders and go Adam-hunting.

If you let them. This is the first big choice in BioShock 2: harvest or adopt. Harvest kills them for a big Adam hit to boost your Plasmids and a massive karma ding that you’ll pay for later. Adopt, and you can rescue them as in the first game — or keep them as an Adam-harvesting helper. “The adoption mechanic, fairly importantly, is a direct rebuttal to the horrible escort quest that you may have played in other games starting with BioShock,” laughs Thomas. It’s not a simple escort mission: whenever a Little Sister harvests a corpse, she draws every nearby Splicer to you, triggering what Thomas calls an “opt-in siege.”

The battle we saw through the helmet of a heavily upgraded Big Daddy in the foyer of Fontaine Futuristics was spectacular. A few minutes’ warning gave time to throw down cyclone traps around the Little Sister before the Splicers came swarming through the doors and windows. The struggle that follows is fast and messy: the player flames one Splicer, lures another into the cyclone trap, only to turn around and see a third hacking at the Little Sister. These “gathering” encounters will be challenging, with large numbers of normal Splicers, but as you progress you’ll meet newer versions that pose even bigger problems.

“Splicers that have managed to survive all this time have had to become apex predators,” describes Thomas, “slowly splicing themselves into something that can survive. There are new Splicers and a lot of them are significant threats to a Big Daddy.”

Sister Act

As in the first game, your actions shape how you progress, and they’ll guide you to planned multiple endings — though this time you get a better indication of which one you’re heading for and have the chance to change it. But one thing you can’t escape is the wrath of the Big Sister. As the new overlord of the city, she likes things just the way they are, and as you separate Little Sisters from their Big Daddies, she’ll start to take notice.

Jordan explains: “When you’ve gone through enough Little Sisters, you have another dynamic encounter with the Big Sister. She’s the one who will hunt you and you have this countdown to prepare; you’ll hear this creepy little-girl voice over the radio noting that the Big Sister is coming.”

This is the true goosebumps moment of the demo — the point where you realize that your big drill might not be the catch-all solution it’s been so far. A shriek in the distance and a whimper from the Little Sister: “Oh, Mr. B., Big Sister doesn’t want you to play with me…” A few minutes of glancing around the bloodstained lobby and she’s there, springing onto the globe in the center and going on the attack.

And it’s fast. Really fast. She leaps insect-like around the room, attacking more quickly and more brutally than the Splicers. She can leap across the room, savage you with the blade attached to her arm, and be away before you have time to land a shot. Then comes her Plasmid treatment: a swirling tornado fills the room, picking up all the furniture and sending it flying directly at you. Game over.

Tell Us a Story

As a mere boss fight, it's gripping stuff, and that's without seeing any standout moments akin to BioShock's stunning Fort Frolic. Thomas was the creator of that, the highlight of the game for many players, and we’re promised similarly powerful encounters — tying action, story, and location together — in the sequel. Expect some haunting settings and unsettling new characters in your travels through the doomed undersea world when the game hits late this year. “There will be surprises,” promises lead level designer Zak McClendon. More people like Sander Coen? “Definitely.”

Like all good residents of Rapture, we’re holding our breath.