I'm surprised that you chose BESW's answer which only gives you an example for how to cite a video game, but does not actually explain what you asked for, namely citing events in a video game.
I'll try to answer that.
To refer to a specific plot element of a video game in a scholarly paper, you need to first identify the structure of the game. Usually games are either structured by "levels" (as in Prince of Persia), location independent narrative or plot (e.g. achieving a certain in-game goal such as acquiring a new party member or gaining a new ability), adventures (that is, complete-in-themselves subplots), or "location" (usually accessible via a map).
So when you analyze video games as a scholar (as opposed to a reviewer or fan), you need to do so in a structured manner and refer to the internal structure of the game, either as it is defined through the publisher (e.g. by map area) or as you have found it through your analysis of the plot. In the case that you refer to a structure no readily obvious to any game player, your paper needs to include the complete structure as a table or appendix, and you can then refer to this depiction of the structure when you refer to an element of that structure.