(Not a one-shot! Clop won't appear until later in the story!)

The time when Twilight goes into heat has arrived, and she has isolated and barricaded herself in the library in order to keep herself from going crazy and seeking out an unwanted mate. No one, not even Spike, is allowed to be in the library.

Twilight's friends are stumped and don't know what to do in order to stop their bookish friend's suffering, but when an old friend of Twilight's arrives without warning, claiming to have the answer, the rest of the Mane 6 and Spike have no choice but to trust her to make Twilight better.

(I don't really know what the right tags for this story would be, so I just put what seemed necessary.)