Warning: This article includes detailed ending spoilers for BioShock Infinite and Burial at Sea Episode 1.

"It's a nice, light, happy ending, right?"

A long six months since have passed since we inhabited the shoes of Booker DeWitt. As Burial at Sea opens we find ourselves back in control of BioShock Infinite's hero, but in a completely different setting and guise. So which version of DeWitt is this, and how does his relocation to the doomed underwater metropolis of Rapture fit with Infinite's narrative? Answers to these questions are slowly teased throughout the DLC's brief but absorbing first episode, before another mind-bending finale from BioShock creator Ken Levine that pulls the rug out from under players entirely.

Infinite's ending involved three versions of DeWitt. There was the aged Comstock, Columbia's creator and Elizabeth's kidnapper - who was eventually drowned by 'our' Booker, as controlled by the player. Infinite's final twist saw this version of DeWitt die too - drowned by a multiverse of Elizabeths to pre-emptively stop all versions of Comstock from ever existing. Which was a bit of a raw deal.

But there was another version of Booker as well - the one who briefly appeared after Infinite's end credits, once the dust had settled on the game's reality-changing antics. With the timeline reset, this DeWitt was back in his old life - possibly with his infant daughter, too - in a reality cleansed of Comstock's interference. As you begin Burial at Sea it's fair to assume that it can only be this version of DeWitt you are now playing, albeit for some reason transported from Infinite's Columbia to Rapture. He certainly didn't originate there - when recalling how he arrived in the city, DeWitt experiences another nosebleed, just as he did in Infinite when his mind created memories to fit the surroundings of a foreign reality.

But - and here we nosedive deep into spoiler territory - Burial at Sea Episode 1's finale reveals this DeWitt to instead be another version of Comstock, one who somehow escaped Elizabeth's purge at the end of Infinite. This Comstock's attempt to kidnap baby Elizabeth ended in tragedy - rather than losing a pinky finger in the struggle with DeWitt, the infant Liz was left decapitated. Distraught and guilty, this Comstock had the Luteces send him to Rapture where he might find refuge. There his memories reset, he had a shave, and he returned to his former persona.

"The trouble of explaining anything when you start to cover off the mechanics is that the true linear understanding of events gets very, very, very complicated." Ken Levine, BioShock creator

So, how was he able to escape Elizabeth's cull of all Comstock realities - and indeed, how he is he able to still exist now the Columbia he came from presumably does not?

"The trouble of explaining anything when you start to cover off the mechanics is that the true linear understanding of events gets very, very, very complicated," BioShock creator Ken Levine tells Eurogamer when we press him for more concrete answers. "Chronology gets very, very complicated. As Einstein says, 'The only reason for time is so that everything doesn't happen at once'. It's a way we perceive something."

Our theory? In moving to inhabit another reality (one previously free from any form of DeWitt) Comstock was saved when Elizabeth pruned the multiverse of all DeWitt-inhabited branches. Elizabeth's appearance in Rapture to end this last backwater of his existence is simply her finishing the job. She's in the debt collection business, she says, here to repay the damage Comstock once caused her by scrubbing reality clean of any remaining versions.

Elizabeth knew this version of Comstock's identity from the start, it becomes clear. This is a much colder form of the once-innocent character who only wished to see Paris, a version whose worldview has been warped by the events of Infinite. Compare her carefree dance with DeWitt on the sandy shores of Battleship Bay with her sad waltz in the dark setting of Cohen's Club, her cold-blooded plot to kill Comstock now in full swing.

Wake up, Booker Burial at Sea begins with DeWitt/Comstock waking and experiencing a coughing fit. A nod to his previous drowning, perhaps? Or him remembering a reality in which he's dead? Whatever the case, it's not Booker suddenly springing back to life, as the DLC's ending proves. "I think everything's open to interpretation, but he's probably woken up at that desk already a number of times," Levine explains. "Although I'm always a little awkward in these situations as I never particularly view my interpretation as important."

Glimpses of where Comstock died appear through Episode 1, which subtly hint at his real persona.

"Elizabeth has a demonstrated ability to be able to see behind and access all of the doors," Levine reminds us. "She's capable of existing in any reality." This ability allows her to play the master manipulator, able to prey on Comstock when he is most vulnerable: in the dank depths of Rapture that foreshadow the city's fallen future and after forcing him to remember the pain of losing a child.

She guides him down there to discover what became of Sally, the little girl who used to come into his place of work and - due perhaps to some stray memory of twice losing a daughter - that he began to take of. Elizabeth has had no hand in what Sally has become - Rapture itself is responsible for that - but Liz makes sure Comstock stares it in the face, and in doing so finally triggers the memory of what he did to her. And only then does she let the Big Daddy's drill bore into him. It is the very opposite of a clean kill. It's calculated, bloody murder designed to inflict as much pain as possible on mind and body.

"You look at the journey of Elizabeth from the girl you met in the tower to the woman standing in front of you at the end of this, with Comstock's blood all over her face," Levine says. "That's a very different person who has been changed by events. To me the question is - what has Elizabeth just done? What kind of person has she become and where is she going? She's concocted this scheme to have Comstock murdered while at the same time nearly burning a little child, leaving Sally to her fate.

"Where does Elizabeth go from there? How does she react to what she's done, when she has time to think about it? That's what is interesting to me - watching the character evolve over time, change from one person to another due to events. You tell me - I don't think she's going to just wake up the next day and it feel like Animal Crossing from now on. There's nothing wrong with Animal Crossing. But the story will continue from there."

Crib notes Was baby Anna in the crib at the end of BioShock Infinite? Levine has previously refused to give a definitive answer. "The question is," he begins, "what would Heisenberg say? Things exist in every conceivable state until they're observed. There is no answer that can be definitive because until they collapse (getting very scientific, or as scientific as a drama student can) until a singularity there is no answer." Levine has admitted to having a personal answer to the question, however. Would care to share now? "No. [Laughs] I don't believe authorial intent matters very much. I believe your experience of the game and interpretation of events is just as valid as mine. Because I'll be dead one day, and if someone is still playing this game after I die then what does it matter what I say? It matters what people experience. It's hard to give any interpretation of that because I don't want to ruin it for people." She totally was.

We've seen Liz stumble down a dark path before - and that didn't end well.

We've known for some time that Elizabeth will take over the game's protagonist role in Episode 2, but only after seeing Episode 1's ending is it made clear how much the whole of Burial at Sea is about her. "Even though this is based in Rapture it is part of the BioShock Infinite story, and really it is Elizabeth's story in a lot of ways," Levine agrees. The revenge mission of which you are the target is a plot device to show how far Liz has been altered. But that's not to suggest DeWitt's presence will be absent from Episode 2 overall. Their story - Infinite's story - has shown their fates to be so closely entwined that it seems unlikely his half is completely done.

It would also be a surprise not to again glimpse Columbia - Infinite's airborne setting that we never really said goodbye to. How about an 'after the fall' version of that? Or a final glimpse, at least, just as Rapture appeared in Infinite? "How do I answer that..." Levine laughs. "Erm, next question? People used to ask me with Infinite if there would be Rapture Easter eggs. The answer was no, Rapture was in it. It was a critical tool we used to explain so much of what was going on in that universe. In the same way, any time we return to something it has to be critical to what's happening in terms of the story and the characters. So I'll say this - if something is critical, it will appear, and if it's not, it won't."

If the story of Burial at Sea is about Elizabeth, then it seems inevitable we'll end up back in Columbia at some point - it's where the character was formed, if not first born. And it would bring a certain amount of closure to the whole Infinite saga, which has to date ended on two satisfying but particularly melancholy notes. Might a more upbeat finale await in Episode 2?

"Booker and Elizabeth's struggles that they go through... the notion of finality and closure get very challenging in these stories because of their infinite nature..." Levine pauses. "I'll say this. I think you'll get a deep level of closure that you don't expect... To be incredibly vague!"