"[Paddy] has a history with Cavanaugh, it turns out, and that is a major reason Maura has to take a step back and choose a side: her biological family or her professional family," Alexander tells. "Whether what happened [between Paddy and Cavanaugh] was done consciously, it's just more proof that Paddy's done enormously shady things in his life and he's not a man that you can trust."
Source: TV Guide