Retrograde amnesia is temporary or permanent loss of memory.

Anterograde amnesia is the temporary or permanent loss of the ability to form memories.

Twilight Sparkle now suffers from the latter of the two. Yet nevertheless, her saddlebag continues to increase in weight, filling up with scribbled-down postulations, warnings of the most unsavory kind, trinkets resplendent with lost meaning, and notes detailing a morning that she will never remember. Does she have the ability unveil the truth with evidence and a steel-trap mind in spite of a severe head injury?

If you wish to avoid spoilers and solve the mystery without the assistance of another, I would recommend you avoid the comments section. I would appreciate it if people left untagged spoilers out of the comment section, but since I know that I cannot enforce that, it's better to assume that every single comment is a spoiler.