an about-face
A sudden, complete turn or change of direction. This phrase can describe one's physical movement or a change in concept. She did an about-face and walked back up the steps once she saw that the subway wasn't running. Based on the reactions we got from test audiences, we need to do an about-face with the movie's plot.
* about-face (on someone or something)
Fig. a reversal of attitude or action. (*Typically: do ~; have ~.) She did an about-face on her rule about not eating in the living room. Now we can do it if we want.