LurkerJ on 27 June 2016
In more than one way, this episode is similar to the Red wedding.
Especially when Catelyn fully grasped the horror that was about to happen, and when it happened it exceeded her (and the viewers) expectations. Margaery found herself in a similar position, but in her case, it was the incompetence of the High sparrow that led to her defeat, actually, her demise started when she was allowed to see Loras in the cell and he asked her to "make it stop, whatever it takes".
