Shay Patrick Cormac (United States Marine Corps), while on a mission for the Assassins trying to retrieve an artifact in Lisbon, Portugal. However, as he took the artifact, the city of Lisbon collapsed, forcing Cormac to leave.
When Cormac arrived at the Assassins headquarters, he was infuriated with Achilles Davenport, the leader of the Canadian, Greenland and New England Assassin's guild. He explained what happened, convening no one of the dangers of these artifacts.
That night, he stole Achilles's maps of the artifacts locations. He was caught by Achilles, forcing him to counter and defeat Achilles in hand-to-hand. Cormac escaped, but was shot by Liam O'Brian, an old friend from Ireland who served in the Merchant Marines. Cormac was taken in by a small family who gave him the uniform of a Templar. In return, he hunted down the criminals who harassed them. Upon capturing the district from the criminals, Shay was introduced to Colonel James Monro, of the British Army, who took great interest in recruiting Shay to fight the criminals. However, Monro would often speak of the Templars, intending to sway Shay over to the Templar cause and fight the assassins and the French Navy.
Shay had, over a long time of service to Monro and Templar order, gained Monro's trust and respect. This was only enhanced when Shay saved Monro's life from Native mercenaries. The mercenaries were led by a Native American assassin that Shay used to be greatly allied with.
Around a year later, Monro and his army were put under siege at a fort in Albany. Shay saved Monro and told him to take a manuscript depicting locations of different artifacts similar to the one in Lisbon, to Shay's ship the Morrigan. Shay notices the leader of the mercenaries is attacking soldiers atop the fort walls. Shay chases him down and kills him. Before his death, the assassin tells Shay that Liam is in Albany to kill Monro while Shay was distracted. Shay sprints to a burning house where he finds Monro mortally wounded by a gunshot in his chest. Shay carries him out, only for him Monro to die, informing Shay that Liam stole the manuscript.