A former co-worker of William Zimmerman, Joe Kavanaugh is a police detective, a hardened skeptic, and someone who simply isn't too fond of Zimmerman or his crazy observations. Whenever a case gets too baffling or unsolvable, however, Kavanaugh begrudgingly realizes how valuable it is to get William's insight. Thus, he often brings William in on cases that involve strange circumstances, the unknown, and Abnormals. This unwittingly helps William do his job to find and rehabilitate scared Abnormals who are on the run.