When a baby dragon starts having dreams about his mother who he has never known, he starts asking questions. However, the pony (Twilight Sparkle) who raised him, refuses to tell him anything.
One day, the dragon is sick of not knowing who his real mother is. He runs away.
He writes all bout his adventure in his diary. when it's all over, he sends a letter to Princess Celestia. The letter contains pages of the Dragons diary and parts of the pony's diary.
This is the letter he wrote.

Join Spike on an adventure to his mother.

update: i started on this even before i knew the synopsis of S02E21

story: chibi95.deviantart.com
idea: whiptooth.deviantart.com
correction: Dragon-guy36.deviantart.com