falter vs lose the plot

falter

verb
  • To hesitate in purpose or action. 

  • To fail in distinctness or regularity of exercise; said of the mind or of thought. 

  • To cleanse or sift, as barley. 

  • To waver or be unsteady; to weaken or trail off. 

  • To stammer; to utter with hesitation, or in a weak and trembling manner. 

  • To stumble. 

  • To lose faith or vigor; to doubt or abandon (a cause). 

noun
  • An unsteadiness. 

lose the plot

verb
  • To lose sight of an important objective or principle; to act contrarily to one's own interests through concentrating on relatively unimportant matters. 

  • Used other than figuratively or idiomatically: see lose, plot. 

  • To cease to behave in a consistent and/or rational manner. 

How often have the words falter and lose the plot occurred in a corpus of books? (source: Google Ngram Viewer )