WARNING: One more time, this ending analysis of BioShock Infinite discusses the game's ending.

Like a ride on one of its soaring skylines, the latter half of BioShock Infinite's narrative is a twisted and breath-taking race through the city of Columbia and beyond, moving on to expand the series' scope to a dizzying scale. It begins and ends with a baptism of Booker DeWitt: his rebirth in one set of timelines as antagonist Zachary Comstock, and in another, his eventual realisation that he must sacrifice his life to stop the former event from ever happening.

After his part in the horrific Wounded Knee Massacre, DeWitt is given the choice to have his sins washed away and be baptised as a new man. In one branch of realities he does, growing rich and funding the research of physicist Rosalind Lutece. Armed with her technology, he is able to create "tears" through into other universes and glimpse potential futures. He styles himself a prophet, and builds Columbia with himself as its figurehead.

Ironically, it is this baptised version of Booker which does not repent for his actions. Buoyed by the fame and wealth generated by his borrowed accomplishments, Comstock arms Columbia as an airborne military might, seceding from the United States as his actions become more extreme. Audio diaries describe how he sees other races as The White Man's Burden, with the fantastically-designed Hall of Heroes level a monument to his racist and jingoistic beliefs. Prematurely aged and sterile due to his frequent abuses of the tear technology, the only thing Comstock wants for is an heir.

This is where "our" Booker comes in. Never baptised, he has lived with his sins for several years. Pained by these memories and the recent death of his wife during childbirth, he is a man ruined by drink and gambling debts. Acting through the male Robert Lutece in Booker's universe, Comstock wipes away his debts in payment for his daughter. She is the heir Comstock never had, and able to naturally navigate the multiverse after a last-minute change of heart from Booker sees the tip of her finger left behind when making the jump between realities.

The priest who baptises Booker on his entry into Columbia is the same man who baptised Booker/Comstock in the past.

Towards the end of the game, players get a glimpse at how Comstock's universe could continue. In 1984, an aged Elizabeth - broken by torture and bent to Comstock's beliefs - would have overseen Columbia attacking New York, raining down fire and setting the city ablaze. Booker's intervention - the journey players undertake from the opening moments of the game - is designed by the Luteces to stop this.

The Luteces are two of the most complex characters in the game. Audio diaries present Robert Lutece as the more unwilling of the pair, wary of the carnage that Comstock's world will face due to their intervention. He presses Rosalind into recruiting Booker for his rescue mission, but the duo are not entirely driven by compassion. Like the late Lady Comstock, they know too much about Elizabeth, whose 'miracle birth' is now a vital component of the Comstock cult.

It's implied that the Booker which players first meet is the latest of many attempts by the Luteces to get Elizabeth rescued. The pair know Booker will pick ball number 77 during the raffle because he always has. His coin toss comes up heads because, as their tally of 122 previous chalk marks show, it always has. These are the "constants" that Elizabeth mentions in the final section of the game, and until now have always ended with Booker being killed by Elizabeth's monstrous mechanical jailer, Songbird.

These moments are also a knowing joke on the player. The Luteces know Booker won't row the boat at the beginning of the game because they've seen it before and know he never rows the boat. Like Booker, the player cannot row the boat either. It doesn't matter whether a player picks the cage necklace for Elizabeth or the bird, or whether they save or kill Slate. There are no lasting differences in the game's ending because the story is destined to end the same way regardless.

Elizabeth eventually shows Booker an infinite sea of lighthouses, an ocean of doors leading to other realities. But many are portals into other versions of the same tale where Comstock is also a threat. "We swim in different oceans, but land on the same shore," Elizabeth says, suggesting a kind of fatalism at work. Like Booker, players have free will to do whatever they like during the game while adhering to its constants. One player will progress through the game in broadly the same way as another and the end result will always be the same.

Music to your ears The splendidly anachronistic music found within Columbia signposts Comstock's use of the reality-bending tears. The tunes are well chosen - the lyrics to Beach Boys' God Only Knows fit the game's story perfectly. I may not always love you But long as there are stars above you You never need to doubt it I'll make you so sure about it God only knows what I'd be without you If you should ever leave me Though life would still go on believe me The world could show nothing to me So what good would living do me God only knows what I'd be without you

Any coin that Elizabeth throws Booker will be caught heads up, too.

Booker is finally able to control Songbird after a visit to a future version of Elizabeth. It is this variable that allows him to begin breaking the loop, and Booker's choice to never emerge from the waters of his initial baptism - to never become Booker or Comstock - that seals it. But despite this new ingredient into the mix, the game still ends up in a place that is signposted from the very beginning, as if Booker was always supposed to eventually take this path.

"Is it possible that the man is simultaneously sinner and saint?" Comstock muses in an early audio diary on baptism, concerning the moment before someone is brought forth from the water. It's one of the first signals of what is to come. "Will the Circle Be Unbroken?" asks the Christian hymn which recurs throughout. "Is a better home awaiting, in the sky?" The game ends with a pre-Columbia version of Booker appearing to hear Elizabeth from the next room, awake in a universe where he could have never given her away as Comstock no longer exists.

Elizabeth defines the BioShock brand within the game: there will always be a man and there will always be a lighthouse. The first half of BioShock Infinite's tale felt tired because it mimicked the games set in Rapture without any deeper explanation. But the second half soared beyond these comparisons by peeling back the series' entire universe. Rapture and Columbia seem like variations on a theme because they are just that.

Of course Songbird was inspired by the Big Daddy. In one audio diary it is explained that Fink designed Elizabeth's captor after seeing another universe's merger of man and machine. It's also unsurprising that Booker can operate Rapture's genetically-coded bathyspheres - he is the equivalent in Columbia to the Rapture reality's Jack and Andrew Ryan.

It leaves the player bewildered as to where the series could go next. After defining the series so boldly, how could a future BioShock up the ante? Knowing that Rapture and Columbia are derivatives of the same tale, could another game support a further incarnation? Any one of Elizabeth's lighthouses may hold another reality, but what lies next is a mystery known only to Irrational - and it's one that we can't wait to begin unravelling.