" lose the plot "

 [ "Lose the plot" ]

1: To stop acting rationally.

  * e.g.,  ... The day of her wedding, I thought Amy was going to lose the plot. 

 [ "Lose the plot" ]

1: Get really angry and lose your self-control. Derogatory, as implies that it wasn't a reasonable reaction in the circumstances.

  * e.g.,  ... After Dad saw my picture on the front of the porno DVD, he completely lost the plot. 

 [ "Lose the plot" ]

1: To lose the ability to cope with or understand what's going on around you.

  * e.g.,  ... Feminist Frequency is complaining about lack of diversity in female character designs in OverWatcth, a game that went out of its way to have the most diversity in female character designs. Way to lose the plot, Feminist Frequency! 

 [ "Lose the plot" ]

1: To lose all self control and go absolutely bonkers. Make stupid and irrational decisions. In most cases only lasts a few minutes but sometimes can be permanent which will require long periods of habitation in psychiatric hospitals with the men in white coats.

  * e.g.,  ... Jimmy will lose the plot when he finds out someone stole his New Kids On The Block album.