You'll start out dazed and confused, something to do with memory glitches.
After a while, you'll wake up on an advanced medical table, the "Animus". You've been kidnapped to act as a test subject.
The machine recalls ancestral memories buried in your DNA.
You'll go through a tutorial, teaching you to walk, run, blend in, kill, etc.
Once the tutorial is complete, you'll be in a cave with some other men. During the conversation you can press any button when the screen has a glitch on it (kind of like static.) The glitch lets you see the cut scene from another perspective.
Press and hold the buttons indicated while moving forward. You'll jump across the beams, over the pit.
Climb up the ladder you come to.
Do a low profile kill, then walk ahead for a cut scene.
Walk down two sets of ladders.
Walk up to the group of men.
When you attempt to assassinate one of them, you will fail.
Platform up the the left or right side, by holding the two buttons indicated.
Climb up the wall using the same method.
Go through the door and climb the next wall you come to as well.
You'll arrive in a village and a man will talk to you.
Run up the hillside, toward the goal on your map.
After a bit, you'll come to a castle.
Talk to the man at the gate and continue toward the castle.
Enter the castle door and go up the stairs.
Talk to the Bureau leader.
Go back down, toward the village. Your friend at the gate will tell you to go help the villagers.
Kill enemies with your sword as you head down to the village.
Once you reach the bottom of the village, they will all retreat.
You'll have a memory fast-forward, taking you back to the gate.
Head toward the castle. Your friend will call you from above in the castle.
Climb up the ladder to reach your friend. He'll climb up another ladder, follow him.
Your friend will direct you to stand on a platform to his right.
After a cut scene, you'll make a leap of faith.
Some hay will break your fall, but not everyone will be so lucky.
Walk across three sets of beams.
You'll reach a wall to scale.
Use your sword on the wall.
It'll set off a trap, defeating your enemies.
The Bureau leader is very upset with your misconduct.