Liam Riley was an Irish immortal, who in August 1776, was one of the British troop contingent with General William Howe deployed to the American Colonies during their Revolution. He was then in search of adventure and glory. Accompanying him was Amanda, a friend who was apparently a camp follower of the British army. Caught in an ambush, the chaos of battle ensued, and Liam shot a young man whom he soon realized was a latent immortal. He knelt beside Sean and told him he would be well, that he'd have more use for a sword in future than musket. Sean's mother, however, screamed from nearby, startling Liam who shot her reflexively. Horrified, Liam rushed to the woman's side and assured her that her son was special and that he would live longer than she could imagine. She touched his face and forgave him for everything. Liam gathered her up and rushed her to the surgeons, hoping that Amanda's experience would help keep the woman alive. Liam prayed earnestly, promising God that if she lived, Liam would give his life to God.
Amanda informed him that the bullet had been removed and she had managed to stabilize the woman's condition. Liam saw this as the answer to his prayer, and left the army to join the priesthood, as he had promised. He realized that war was not an adventure, and he laid down his sword, leaving it on the battlefield. Amanda pointed out that he had forgotten it, he assured her he had not.
In 1998, he was assigned to the church of St. Julien-le-Pauvre. His old friend Amanda visited him and asked him for a list of doctors operating illegally because she was looking for the injured Nick Wolfe. Liam was able to help her. He also provided old maps of the catacombs beneath Paris, which he still had from the days of the Resistance. He only agreed to provide Amanda the maps in her search for the immortal,Andre Korda, however, because he had renounced violence and did not intervene in disputes between immortals. But Nick Wolfe proposed a deal; if he made a clean basket on Liam's basketball court in one try, they got the maps. Liam agreed and Nick came through.
Months later, Liam read a news report that a painting by Ravelli had been stolen, and that Trevor Benton, who had often donated for charitable purposes, offered a million dollars reward. He then went to Amanda to ask her to return the painting and if possible to donate the reward to the church. Amanda protested her innocence. Shortly afterward he revisited Amanda and she told him that Jade would probably have the picture. Liam knew about the centuries-old rivalry between the two, but his church desperately needed a new roof. So he finally gave Amanda Jade's address. After Amanda and Nick had acquired the painting, Liam got the money for his church.
At the beginning of 1999, Riley was taking care of a young girl who would one day be an Immortal. She knew nothing of the immortals, but she kept a protective eye on Liam. She helped him at work around the church. Amanda appeared one day for some advice. She feared that the next she confronted the immortal, Derrick Markham, one of them would not survive.
Some time later, Liam and Nick were playing basketball when they were visited by the reporter, Lizzie Tynan. She was trying to get Liam to talk to her about exorcism, but he refused. Leaving, Lizzie ran across a duel between Amanda and Sean, whom she was trying to keep away from Liam. Sean wanted revenge for his mother's death 200 years previously. Liam refused to fight, however, because of his battlefield promise, but he then found from Amanda, the woman for whose salvation he had devoted his life to God, died two days after she'd been shot when infection set in.
Liam was angry that Amanda had lied to him for over 200 years, and he had a crisis of faith; he was ready to give up his vocation. But Amanda, by threatening first Liam and then Lizzie, made him finally realize how deep his faith really was.
When Sean returned, Liam met him unarmed and unwilling to fight. Sean was unmoved and promised to take the priest's head. Liam knelt before him and forgave him. Furious, Sean asked what gave him the right to forgive him, Liam replied Sean's mother had when she had forgiven Liam. Sean left the priest alive.