Aid and abet is the term used to describe the process of a person knowingly helping another person evade the law when they know that the person is wanted by the police and that their actions will undermine the police's ability to find the person. The act of aiding and abetting is a felony crime and can be punished with several years of incarceration and even an open-ended incarceration based on complying. The person could be held in jail potentially forever until they agree to tell the courts what they want to know; in most cases, it is the location of the absconding felon.
A person can only be charged with aiding and abetting if they actually know that the person they are helping is on the run. If they do not know, they would be considered to have been taken advantage of and unknowing.