Aiden trained alongside Emily under Takeda. They met when their missions conflicted in their search for a Russian gangster. Aiden believed the man to be responsible for the disappearance of his sister while Emily was under orders from Takeda to apprehend him. After shooting the gangster, Aiden returned to Takeda's training with Emily. Eventually the two became involved in a romantic relationship. Despite promising to take Emily with him, he left without her to find his sister. When Gordon Murphy attempted to kill Emily, Aiden killed him. Emily rejected Aiden's attempts to reconcile, but at the end of "Penance" he came to check on her and they rekindled the spark. Since then, they have shared many tender moments. Daniel, unaware of the plots in which the two conspire, has been working with Aiden to replace his father as CEO of Grayson Global. He also views Aiden as a competitor for Emily's attention.

Later, Daniel finds out that Aiden's father, Trevor Mathis, was a baggage handler suspected of putting a bomb on "Flight 197". Daniel fires Aiden and then they become enemies competing for Emily's heart. This leads to a fight between the two of them in the season finale resulting in what appears to be Aiden's murder. Aiden later returns in season 3, revealing that he survived a gunshot wound from Daniel. He continues to work alongside Emily in her revenge against the Graysons, even pretending to help Victoria for her. In the Season 3 finale Victoria smothered him to death.