[s5e4] Memoirs Of An Invisible Dan -
Initially, the group tries to be supportive, but as they actually read the book, the "fictionalized" portrayals prove to be devastatingly accurate and cruel:
Dan writes that he and Blair had sex, a revelation that nearly ruins her engagement to Prince Louis. [S5E4] Memoirs of an Invisible Dan
His character commits suicide and dies alone, leading Chuck into a period of deep introspection. Initially, the group tries to be supportive, but