Some researches state that discovering what to say is part of the writing process. We are interested in studying this aspect of writing within the scope of computer models. MEXICA is a computer model for plot generation which, inspired by the idea of the discovering aspect of writing, avoids the use of predefined story-structures and explicit characters’ goal. This work claims that abduction is an important part of the process of discovering what to say and therefore computers models of abduction for automatic plot generation are an important topic to be studied. This paper describes some basic concepts about abduction and how they are implemented within the MEXICA program.