Instructions
Play through the game until you have completed Memory Block 2, wherein you assassinate Tamir. Speak with Lucy when you leave the Animus, then walk up to her computer and press "X" for the PS3 or "A" for the Xbox 360 to interact with it.
Access Lucy's computer to read her E-mail any time when the two of you are alone in the lab or when both Lucy and Vidic are out of the room.
Play through to the end of the game, when you kill Al Mualim. When you leave the Animus, there is a scene between Lucy, Vidic and some nameless men in suits. Watch the scene and use your Eagle Vision to see hidden messages and pictures covering the walls and floor of the lab.
Wait until Vidic and Lucy leave the lab, then go into your bedroom. Look at the wall behind your bed and use Eagle Vision again. You lose control of Desmond as he looks at the wall and starts asking questions, then the credits roll.
Wait until for the credits to finish rolling. When the credits are done, you regain control of Desmond. Walk back out into the lab and use Lucy's computer near the Animus. Read the message in the "Deleted Items" folder for hints about the events of "Assassin's Creed II."