In Assassin's Creed, Altaïr's memories are solicited by Abstergo in their attempt to find the Piece of Eden. Altaïr, still in Jerusalem, ventures to Solomon's Temple to confront crusader Robert de Sable and retrieve the Piece of Eden for Al Mualim, head of the Assassins. Betraying many tenets of the Creed of the Assassins and failing his mission, Altaïr is demoted to a novice assassin upon return to the Assassin's Fortress. To redeem his previous status, Altaïr is sent by Al Mualim to assassinate nine targets in three different cities.
With each kill, Altaïr learns there is a connection between his targets; they are all Templars united by Robert de Sable to take control of the Holy Land by force, although they all claim to pursue a noble goal. After assassinating all nine targets and discovering that his ninth target was in fact a trap, Altaïr confronts Robert in front of King Richard, leader of the Crusader army. Altaïr informs Richard that Robert is plotting to betray and kill him, which causes him to encourage a duel to the death between Altaïr and Robert.Richard then believes Altaïr. Upon dying, Robert confesses to Altaïr that they were not nine, but ten Templars. The tenth being Al Mualim, who wanted to keep the Piece of Eden for himself and therefore sent out Altaïr to kill the others. Back at the Fortress, where Al Mualim had taken over the minds of the people inside, Altaïr manages to defeat and kill him in a duel.
The memory Abstergo was searching for, which located the Piece of Eden, reveals it is only just one of several, the "Apple of Eden", and that over fifteen different other Pieces are scattered across the world. Back in 2012, Abstergo sends a team to recover as many Pieces as possible. Deciding they do not need him anymore, they give orders to kill Desmond. Lucy Stillman, an Abstergo employee who revealed to Desmond that she is an Assassin, convinces them not to kill Desmond until they recover the Pieces, buying him time. Desmond is left alone in the Animus room, and by the use of Altaïr's Eagle Vision inherited from the 'bleeding effect' caused by the Animus, he sees many symbols drawn in blood on the wall in his room and on the floors of the lab.