The animus malfunctions and you get sucked into different time period travelling the world and meeting up with characters from the universe.
Since nothing exciting is happening in the modern in the game why not add my own spin...
It's based on an alternate universe- Desmond didn't die in 3 but did shortly after defeating Juno. Lucy didn't die in brotherhood but was wounded- she blamed herself for what happened in Brotherhood and revelations and Desmond kept her secret. Hera is now the major threat.
In each period the scenario changes- in the most cases he is himself under a different name and the characters acknowledge he is different. however in some periods he plays a character for e.g. he is an Templar that helps Evie out.
Some occasions it is set after the game settings and sometimes he meets the assassin's others he doesn't.
Each story will have one option for the character to stay another with an option to either go back to the present and/or jump to the next period.
Some will be more detailed/options based then others e.g. odyssey/Greece.
In each story people may have changed: If you have played Red Dead 2 John is good- my version he chooses to ride with Dutch over looking over Abigail and Jack
Same applies to GOT: Cersei is evil?- my story includes examples and reason for this and her link to a first civilisation god that causes this.
Khaleesi and Jon are also shown in some accounts/version from the other sides POV so to them are evil.
