He was an IRA terrorist, who fled from his former life because of the madness of his mentor, who, in his madness regarding detonating bombs, even killed his own sister, who was also his girlfriend, when Liam wanted to stop him from detonating one.
Now he is a bomb deactivation expert in Boston fighting for redemption because of his past and is also married with a child.
Now his mentor has returned. He blames him for the detonation, which killed his sister and destroyed his life and, hellbent on revenge against him, he wants to destroy everything dear to him. However, no one must know what is really going on between them.
He manages to stop him and save his family.