Follow Elise and investigate the workshop, then defend her and kill the shooters.
Assassin's Creed: Unity guide - Sequence 7 Memory 1: A Cautious Alliance
If you haven't been using stun bombs, make sure you have a couple in your inventory and know how to select them quickly. It's worthwhile knowing how to use bombs effectively, so it's good to see the challenges highlighting different aspects of combat. Remember to hit the grenade button once only; it's easy to miss the animation and spam the button, wasting your precious supply.
- Three enemies incapacitated with Stun Bombs
- Three headshots
Once again we find ourselves chasing Elise. It's not hard, as she takes a pretty easy street-level route for the most part.
Investigate the Workshop
Remember this place? We're back checking out Germain's workshop. Climb up to the room marked on your mini-map and walk about a bit until you get a cutscene.
You're being ambushed, but you know what to do: stun grenades. Don't kill anyone until you've stunned them, starting with the two enemies that come at you (let them close on you and you can get them both in one hit) and then dropping one at the feet of Elise's opponent. As soon as you stun him she'll go right for the throat. I like her. Your reward is another cutscene.
Kill the Shooters
As soon as you come under attack, drop into cover under a window. There are three snipers to one side and two in front, so you'll need to move around the room and re-enter cover. Use whatever ranged weapon you like (I don't recommend berserk blades) and use free aim to score three headshots for the optional challenge, or five headshots because you're a badass. Once everyone is down, you'll have completed the mission.