Complete the Prologue and enjoy the video about Helix. You may only see it once. Normally, the achievement will unlock by the time you take control of Arno.
---"But PaleGringo... it didn't unlock"
I started playing this game simultaneously with the Mrs. on November 24, 2014. She got this achievement when she completed the prologue, and I did not. After getting all the other achievements in the game, however, I was able to get this one by precisely executing the following 10 step program:
1. Guide Button > Menu Button > Quit Assassins Creed Unity
2. Menu Button > Manage Game > Press A on your Saved Data (100+ KB)
3. Delete from console. IT IS IMPORTANT TO NOT DELETE EVERYWHERE
4. Settings > Network > Go Offline (This will prevent your XBL save from synchronizing to your local box)
5. Launch Assassin's Creed Unity and play through the Prologue as normal.
6. After ...
... Guide Button > Settings > Network Go Online. In a few moments after resuming the game, the achievement should
Now... to get your save data back
7. Guide button > Menu Button > Quit Assassins Creed Unity
8. From the Guide, Menu Button > Manage Game.
9. Again, delete your Saved Data file (64.4KB when I did it this time)
10. Start Assassin's Creed Unity. You should
see a "Synchronizing" screen pop up as your XBL file is copied back to your box. Voila... the 1% of us that never got this achievement will now have it.
Message me on XBL or on here if you need some help or are unsure about any of these steps. Happy assassinating!
PS4 version of the Prologue is embedded below.