Sean is a teenager who is recruited in the team of the mysterious Monroe because he has ancestors involved in the Assassin-Templar war. At some point during his childhood, Sean had an accident which left his legs paralized.
According to Abstergo, Sean and the other recruits of Monroe were part of what the Templars researchers called an "Ascendance Event"; multiple bloodlines who had been in contact with Pieces of Eden mysteriously converging at some point in history as if they were guided by an unidentified force.
Recruited by MonroeEdit
At some point, Sean heard about Monroe, a discreet It guy who was known for offering free Animus sessions to willing youngster. Sean used the Animus as a way to escape his wheelchair by experiencing the memories of one of his ancestors, an Irish farmer, walking again through him.
In 2016, Sean was contacted by Monroe who asked him to join a group of other teenagers who like him had Templar or Assassin ancestors, in order to find a Piece of Eden, the Trident. The group, which in addition to Sean was composed of Owen, Javier, Natalya and the siblings Grace and David, accepted after Monroe told them about the secret war and his wish to hide the artifact from both the belligerents.
Under the guidance of Monroe, Sean and the other teenagers successfully discovered the clues leading to the location of the artifact while exploring the memories of their ancestors during the New York City draft riots of 1863. In the case of Sean, his ancestor was New Yorker Tommy Greyling, a former Union soldier turned policeman who unknowingly witnessed the fight between the Templars and the Assassins for a part of the Trident. While reliving the memories of Greyling, Sean also witnessed his ancestor falling in love with singer Adelina Patti while protecting her during the riots.
However, as the team eventually discovered that the Trident prong was in the house of the late Ulysses S. Grant, a Templar strike team assaulted the warehouse where they were using the Animus. Sean and three other teenagers, Grace, David and Natalya, were captured and brought to The Aerie, where the Templars Isaiah and Victoria Bibeau tried to convince them to help their Order. At first reluctant, Sean was eventually seduced by the Templar ideals and decided to trust them and help Abstergo find the Trident.
Working for AbstergoEdit
Later and now working with the Templars, Sean had to relive again the memories of Greyling, this time in 1872. Now a Pinkerton detective, Greyling went to London in order to catch a Templar murderer and became involved with Assassins Evie Frye and Henry Green.
- After they both relived their ancestors memories and feeling Greyling falling in love with Natalya's ancestor, Adelina Patti, Sean developped a crush for the girl.