lose the plot

lose the plot (third-person singular simple present loses the plot, present participle losing the plot, simple past and past participle lost the plot)

1. Used other than with a figurative or idiomatic meaning: see lose,‎ plot.
   • 2005 Winter, Alan Palmer, “Intermental Thought in the Novel: The Middlemarch Mind.”, in Style, volume 39, number 4, page 427:

     Readers enter the storyworlds of novels and then follow the logic of the events that occur in them primarily by attempting to reconstruct the fictional minds of the characters in that storyworld. Otherwise, readers lose the plot.

2. (Britain, idiomatic) To cease to behave in a consistent and/or rational manner.
   • 2004, Ron Phillips, The Travels of Plymouth: A Fable for Our Time, page 202,

     Right then I lost the plot. I did, man, I went over the edge.

   • 2007, Caryl Wyatt, Anita Le Roux, Look Me in the Eye: Caryl's Story, page 28,

     Finally, I lost the plot. I got into my car and drove to the police station.

   • 2010, Jackie Hall, The Happy Mum Handbook, page 102,

     Apologise for losing the plot and explain what made you react the way you did.

3. (Britain, idiomatic) To lose sight of an important objective or principle; to act contrarily to one's own interests through concentrating on relatively unimportant matters.
   • 1995, John Frank Williams, The Quarantined Culture: Australian Reactions to Modernism, 1913–1939, page 219,

     But while there remains a considerable degree of consensus that the consequence of apparently losing the plot sometime between 1914 and 1918 was the cultural and economic malaise of the 1920s and 1930s, there are still some who look back on the interwar years less with criticism than with nostalgia.

   • 2007, Colin James Isbister, The Body of Christ, page 99,

     Because of this it seems to me that we have somehow lost the plot and we're in desperate need of balance. The idea of Protestant ministers touching the body of Christ (the bread) with great love and tenderness like the priest described is almost incomprehensible.

   • 2011, House of Lords Select Committee on Economic Affairs, 2nd Report of Session 2010-11: Auditors: Market Concentration and Their Role, Volume II: Evidence, page 19,

     [Professor Fearnley:] If I can perhaps be a little unkind about my profession — which is fair enough I suppose — I think the accountancy profession, along with other professions, loses the plot from time to time and has to be pulled back from what it was doing before.