The sunset stained the water as she held him under, adding color to a bloodless death. He did not resist consciously, but when that consciousness left him his body took over and struggled vainly, so she pushed harder. Eventually the struggling ceased.

She sighed, and reflected on the finality of the action. Booker DeWitt was dead.

Beside her, the virtual rainbow of doppelgangers began to disappear one by one like grapes being plucked from a vine, vanishing from the realm of possibility as the ripples of her actions spread into infinity. The chain of events had been broken, and therefore they could no longer exist. Soon she would vanish into oblivion as well. She closed her eyes, waiting for the nothingness to claim her.

It never came.

She blinked, opening her eyes to find the same scene before her as when she had shut them. Booker's still form lay beneath the water, a monument to a sacrifice of his own choosing. Without the decision that had created such a radical divergence in timelines, there would be no Columbia. There would be no Father Comstock. There would be no Elizabeth.

And yet she remained.

"Why?" she accused more than wondered. "Why do I still exist?"

"Because, little lamb," she heard a voice say behind her, "You're the one holding this little corner of the multiverse together."

Elizabeth turned around and came face to face with Robert and Rosalind Lutece.

"What does it take to make you two go away?" she nearly snarled, thoroughly fed up with their ability to show up precisely when they were neither wanted nor needed.

"See, I would have thought she'd be glad for an explanation," said Rosalind.

"Well, she has already figured out most of it herself," replied Robert.

"Quit talking like you barely realize I'm here!" she shouted, and they returned their attention to her. "Why haven't I disappeared yet?"

"Weren't you listening the first time?" asked Rosalind. "I do so hate repeating myself."

"Perhaps an elaboration might do her some good," her counterpart suggested. "The finer points of trans-dimensional science still haven't become clear to her."

"Very well," the scientist said. "Perhaps we should start with what happened to your alternate selves."

"I already know what happened," asserted Elizabeth. "They disappeared into nothing after I broke the chain of events. If Booker never decided to become Comstock, that means none of this ever happened."

"Not precisely," she corrected. "You eliminated that particular chain of events, but you're forgetting about the paradox."

"Paradox?"

"She means that if you never experienced those events, what reason would you have to erase them?" Robert chimed in. "What actually happened is that you eliminated every version of the timeline that happened save your own."

"Exactly," she agreed. "You condensed the infinite into one. The other possible outcomes were eradicated and assimilated into the trans-dimensional energy for which your body is a conduit."

Elizabeth stared at the two of them in confusion, though their explanation made some amount of sense. "What do you mean, I'm a conduit?"

"You didn't actually think Father Comstock kidnapped you because of your abilities, did you?" Rosalind asked dryly. "The truth is my machine already enabled him to travel across dimensions. Comstock used it to peer into dimensions that were a little further along than our own and pass himself off as a prophet. But the machines turned him sterile so he found an alternate dimension where he already had a child."

"I know that," she replied. "He stole me from there and then later you travelled back to that dimension and took Booker into Comstock's dimension so he could kill Comstock after he murdered the two of you."

"Yes, well, when the dimensional portal severed your finger, it also opened a channel for trans-dimensional energy and granted you limited control over it," said Robert. "That was when we began work on the Siphon."

She glared. "You mean that machine you used to keep me prisoner so I couldn't create new tears?"

"That wasn't entirely it," Rosalind clarified. "Trans-dimensional energy was especially hard to come by, and I needed it to power my machine. The Siphon proved a much more efficient means of procuring it."

"I'm afraid Comstock is the one who used it to keep you on a rather tight leash," her "sibling" said. "The machine was never intended to operate at the level that he and his scientists tuned it to. You could well have continued creating tears into adulthood, given how quickly the energy was flowing in."

"But Comstock wanted to keep you all to himself," finished Rosalind.

"No surprise there," said Elizabeth. "So, what? I'm just doomed to live the rest of my life on my own then? After what I've seen, I'd rather just vanish into nothing."

"Well yes, but if that happened, you wouldn't be the only one to vanish," the scientist replied. "The amount of trans-dimensional energy you hold is great enough that if you were to no longer exist, it would have to go somewhere."

"And it would consequently destroy everything in its path," added Robert. "Without limiting itself to a single dimension either."

"So I'm a living dead-man's switch?"

"More or less."

Elizabeth frowned. Understanding began to awaken within her as she peered across dimensions, and her eyes widened as she became aware of what was happening.

"Should we tell her the best part?" asked Rosalind.

"I think she's starting to figure it out for herself," her twin replied.

"The paradox," Elizabeth said as the pieces started to come together in her mind. "If Booker died in the past then I wouldn't exist, but if I do exist, then that means..." She shook her head. "No, that still makes no sense."

"Very little does when you're working with Quantum Mechanics," Rosalind said. "Moving across space is all well and good, but once you throw time into the mix it becomes rather like a pretzel. Sometimes to avoid one paradox, the time-space continuum will allow another."

"And don't forget," added Robert, "In most versions of the timeline, Booker DeWitt was baptized in the water..." He gestured behind him.

"And emerged…" continued Rosalind, and they each stepped to the side.

"As a new man," they both finished as Booker DeWitt stepped between them scratching his head.

"Elizabeth?" he asked, dazed. "What the hell just happened?"

She did not answer him with words, but surged across the distance between them and enveloped him in a hug. "Mr. DeWitt!" she shouted joyfully.

"Call me Booker," he replied, more on instinct than anything else.

"I'm afraid it's all rather complicated," said Rosalind in response to his question. "But thanks to her powers I'm certain she understands it far better than either of us do."

"So she can most likely explain it to you," finished Robert. "Do take care not to strain causality any further than you already have."

Before Booker could reply, they disappeared.

"The hell was that?"

Elizabeth chuckled. "Don't worry about it," she said. "The important thing is, there's only one timeline now, and we get to decide where it goes from here."

"And where is that?"

"Anywhere we want," she answered, smiling. "The possibilities are endless."