There is a world where Booth never met Brennan.

Brennan dies in her lab, alone, from a heart attack when she's nearly fifty. Angela and her assistant Zac are the only ones at her funeral.

Booth is killed in a stupid accident, walking in on a convenient store mid-robbery. He takes two of the robbers with him. His son cries at his funeral. His brother stands in silence.

There is a world where they only worked together once.

Brennan wrote one book and stopped.

Booth never learns the difference between a squint and his squints.

There is a world where they had frantic sex after their second case.

Brennan was flushed with success and still a little scared, feeling the gun kickback all the way up her arm.

Booth is expecting more then he gets, still not totally used to the logic that Brennan defines her life with. Things fall apart like ice shattering. They weren't ready.

There is a world where Booth takes Brennan into his bed after she finds her mother in limbo

Brennan comforts herself with him, breathing him in, taking it all. When they're done she cries against his chest, soft and without sound.

Booth knows this second the first tear hits his skin that this won't happen again. He forces himself to be okay with it, knows Brennan won't be able to take the chance of being this vulnerable again, and when Cam comes to the lab he grabs onto her like a life ring.

There is a world where Booth married Cam and Brennan married Sully.

They only cheated on their spouses once.

They broke contact the next morning, both of them unable to bear the thought of it. Cam and Sully were very careful to never ask.

There is a world where Booth was really shot, where he really died, and Brennan really buried him.

Brennan never worked with the FBI again.

There is a world where Zac's betrayal pushed them into bed.

Brennan cried, soft and silent, when he kissed her, while he was in her, and after, wrapping herself around him for barely a minute before asking him to leave.

Booth knew she'd never trust him now. He doubted she'd trust anyone ever again if he left. So he stayed, and let her sink her poison into him, drawing it out of her the only way he knew how. They never spoke of it again.

There is a world where they're killed together by sonic waves while working on a case.

Everyone mourns.

There is a world where Booth never comes out of the coma, where he loves his new world too much to leave.

Brennan mourns, because she can't understand, and writes him more and more books, detailing their lives for him.

Booth wastes away slowly, always smiling, just a little, until he slips away, Brennan reading out-loud next to him all the while.

There is a world where Brennan takes a gamble.

Then there's Iraq, then the Maluku Islands. The relationship is new, brand new and fragile, and the stress shatters it like candy floss.

There is a world where everything works out as it should. And they are happy. Together.