Shaun Hastings is an Assassin and historian.
Some time after their escape from Abstergo Industries, Lucy Stillman and Desmond Miles were joined by Shaun and Rebecca Crane, who accompanied them as they traveled in an unmarked truck. Shaun and Herman Geier were in the front. During their journey, the Assassins were attacked by Templars, who forced their vehicle from the mountain road they were on and shot their driver. Shaun, Rebecca, Desmond and Lucy fended off the attack.
Geier suggested that Abstergo had planted a bug on them, which they scoured the truck looking for, finding nothing. After Desmond had relived more of Aquilus' genetic memories, he made everyone stop and get out of the van, where he asked for Shaun's gun and shot Geier in the leg. They used a phone taken from the body of one of their Templar attackers and dialed the last known contact, causing Geier's phone to ring. Desmond killed Geier with a bullet to the head, and they continued on their way to Monteriggioni.
In the Villa Auditore, Shaun researched more about the ancient branches of Desmond's family tree, finding traces of Lugos. Knowing he was an ancestor to fellow Assassin Stella Crow, he called her for help, but she instructed him to drop the matter and leave it to her. After Desmond discovered the location of the Ankh, the Assassins discussed what their next step would be, when they were interrupted by a call from Crow and the arrival of Jonathan Hawk.