The game follows Assassin's Creed , where Desmond Miles is abducted by a mysterious organization in 2012. They attach him to the "Animus" device, which allows him to experience the memories of his ancestor, an assassin named Altaïr. The reconstruction of Altaïr's memories is vital to the captors.
Desmond travels back in time to the Holy Land in 1191, during the Third Crusade, and experiences the events through Altaïr's perspective. Al Mualim, the leader of the assassins, orders Altaïr to kill nine prominent historical figures who are believed to have contributed to war and corruption in the Holy Land.
Players control Altaïr for most of the game, but also switch between controlling Desmond when he is not in the "Animus". This allows for a unique perspective on the gameplay and story.
The game features innovative freedom of choice and movement mechanics. Players can use architectural details like window ledges and carvings to navigate and engage in intense chase scenes if necessary.
Players must gather information about their targets through various means, such as eavesdropping, interrogation, and pickpocketing. This information allows them to choose whether to take on the targets with stealth or full frontal assault.
The outcome of these choices affects the gameplay and encounters with civilians and knights in the cities. Players must balance their objectives with the need to avoid detection, using Altaïr's arsenal and combat skills to overcome challenges.