An escapee is someone who has escaped from a place — often a prison, a camp, or somewhere they were being held. It names the person, not the act. The tone is a little official or journalistic: news reports and forms like escapee; everyday talk often just says escaped prisoner or the man who got away. Though actually it is not only for criminals: a prisoner of war can be an escapee, and people sometimes stretch it, with a smile, to a child who has slipped out of the house. It is almost always a person, not an animal (for animals we more often stay with escaped). The ending -ee here marks the person tied to the verb, like employee or detainee — though actually -ee is messy: sometimes that person receives the action (employee), and sometimes, as here, they are the one who did it.