Sometime afterwards Arno rejoined the Brotherhood, eventually becoming a Master Assassin. He frequently visited Élise, blooming her grave, and proclaimed himself redeemed of his previous mistakes. During the following years while undergoing several missions for the Brotherhood, Arno also tried to honor Elise's last will of reducing the gap between the Templars and Assassins.
On 24 December 1800, Arno prevented a royalist assassination attempt on Napoleon involving snipers, as well as an explosive device known as the Machine Infernal. Arno managed to assassinate the snipers before they could fire at Napoleon's carriage. The Machine Infernal was detonated too early, away from Napoleon's carriage. Arno tracked down the royalist leader behind the assassination attempt and assassinated him and his henchmen.
In 1808, Arno entered the Temple once more, accompanied by Napoleon. There, they discovered Germain's corpse which had long since decayed. They then buried his skeletal remains in the Parisian catacombs. (As seen on Later Life.)