Dipper Pines was very, very relieved that he was home alone when a huge envelope from Gravity Falls addressed to him arrived unexpectedly one September morning. A package on its own would excite him enough, but the fact that it was send by Wendy made him absolutely ecstatic. Had he was not alone, Dipper would be under constant barrage from his parents about getting correspondence from a girl, and had Mabel seen it, he would get teased ad infinitum by all means possible, most of them somehow containing glitter. Suffice to say, Dipper could express his emotions in only one way.

- Boy, uh, you can scream later all you want, but you have to sign this form. - said the terrified mailman, bringing Dipper back to his senses.
- What? Oh, yes. Thank you!

Truth to be told, the entire conundrum made the mailman curious in how long would the young boy celebrate getting this peculiar package, if he didn't had to continue his job. He was about to go along, when he realised that his left leg was being gnawed on by a very nasty pig-looking dog.

It had to be the Pines' house.

Safely in the retreat of his room, Dipper sat in his desk and carefully opened the brown envelope, wondering what Wendy could have sent him. His first thought, given the size of the package, was that she sent his hat back and demanded hers in return. What if it turned out that he had lice, or something?
His horrifying prediction did not came true, as inside was a tied pile of what appeared to be his own dusty notes, together with a smaller, white envelope. Upon further inspection, it contained only two words.

Have fun!

Growing steadily more curious of the contains of the mysterious wrapper, Dipper slowly opened it and pulled out a neatly folded piece of paper. Even before unfolding it, Dipper could see the black ink seeping through the paper, and when he finally did it, he understood why Wendy had to write so tightly. His eyes went wide open as Dipper understood that he received the best possible present he could.

A coded message.

Once he calmed down from his initial excitement, he started wondering how Wendy could have achieved this. However, a quick shuffle through the notes she send back solved the easier of mysteries - most of the sheets of paper contained his many attempts at decoding the messages left in the journals. Several of them were meticulously filled with diagonals of repeating letters, forming a square, that he had to redo every time he thought of another code-word that might be the correct one. Rows underneath them were dotted with long lists of seemingly random letters, together with corresponding list of fully deciphered phrases, as well as dozens of failed ones.
Dipper browsed through them, wondering how on Earth Wendy could have found them - he was sure that he disposed of them once the identity of The Author stopped being an issue.

Shaking that thought off, he took a clear sheet of paper and begun the same complicated process that he was so accustomed to. His first, and only job was to find the code-word - a word that acted as a key, shifting each letter of the original text by the number derived from the code-word's position in the alphabet, cycling through another copies if necessary. As a result, decoding was as easy as subtracting one number from another. The problem was that no one knew the middle numbers.

Dipper started by testing some of the tables he has already made and got teasingly sent back, but none of them worked, producing only gobbledegook. He then tried a few more common words Wendy might have used - their names, their favourite activity ("Movies"), her favourite colour ("Red"), his favourite colour ("Wendy Red") and a dozen of others related words.
It was then when Dipper realised what he was trying to decipher - a letter. Which, though rare nowadays, usually started with the word "Dear", followed by the recipient's name. And sure enough, the first line of the text had ten letters.


Dipper quickly converted "Dear Dipper" into numbers and saw what kind of code-word might lie hidden in between the cipher- and plain-text.




Once the realisation hit Dipper, his head slowly plunged to the pile of papers on his desk, followed by a muffled groan of mixed relief, anger and embarrassment. It wasn't the first time that a keyword was something so monumentally obvious it seemed impossible for Dipper not to get it, but his brain must have taken extra long break if he couldn't notice one right in front of him.
Reconciled with his own imperception, Dipper begun translating, one by one Wendy's message

Dear Dipper,
Yesterday I was cleaning your room in the Shack - not because I wanted to, Stan made me - and found some of your stuif behind the bed. You know, living with three brothers makes you learn the "if no one sees it, doesn't exist" style of cleaning, but I seriously hope your room in Piedmont doesn't look the same.

Dipper promptly stopped reading and took a nervous glance down the dark abyss of the space next to his bed. People were saying that some things are never lost, and probably they were the same ones that actually remembered about spring cleaning. He tossed that thought aside, probably in the same manner as rest of his belongings, and went back to deciphering.

I did not know if you will need any of these papers, but I found that some of them had these code tables, so I declded to try my best at your hobby. If you are readtng this, then it means I'm not a complete failure!

Wendy was right on the spot, as Dipper was actually quite proud of what she has achieved having only his messy notes as a guide. She made a couple of mistakes here or there, but she definitely got the hang of it much faster than he did, which Dipper welcomed with a mixture of astonishment and an alpha-male-position-threatening jealousy.

I've also found your letter to me, which I assume you wanted to give me at some point.

Upon reaching this part, Dipper froze. He knew what kind of letter she might be writing about, and sure enough, after some nervous shuffling, he found his pitiful love confession at the bottom of the pile she send him. It was not just the final letter, if one can call three sentences that, it was all of his previous versions of it that made him even more embarrassed. Reluctantly, he started reading some of them, opening a serious of even more painful wounds from the past summer.

He started with a confident and bold "Dear Wendy", and then his thoughts dissolved into a confused mess of mixed honesty and fear. It would seem that the phrases that could barely leave his mouth were much easier for him to write down, though he was still befuddled from the emotions that enthralled him.
The word "Love" was the first to caught his eyes, as he scribbled it in more than a few places, but then shyly crossed them and replaced with "Like". The next few sentences were too messy to read even for him, but a few words about Wendy's apparent beauty and coolness were readable. His mood did not improve upon remembering that he had to resolve to making an alphabetical list of her traits in order to clear his mind. He then noticed the word "swimsuit" and decided not to read further, hoping that Wendy did the same, otherwise she would have learned more about herself than she wanted to.
The "final version" of Dipper's love letter was composed of just three lines, ending with "I like you", written in thick, black letters, followed by much humbler "Is that crazy?".

The lovesick boy sighed, and defeated once more by his own actions, took the encrypted message and letter by letter begun to read further, expecting another harsh slap of reality just like the one he has already received once this summer. He learned that this kind of bitter medicine is not supposed to linger in your mouth, as the taste might be left for far more than you might like.

Dipper, I know that things did not exactly went the way we wanted to, but what I want to say is... don't worry, man. Liking me is no more crazy than anything we've done together throughout this summer. And I already miss you, so I hope you're not gonna make a girl wait too long. See you next summer, man! Yours, Wendy

Wendy put her pen down and stretched her arms. She couldn't remember last time she paid so much attention to writing - her notebooks usually looked like mess, and she definitely did not write in cursive. This time she even kept her back straight, and that didn't happen since, well, she had someone that actually cared about her posture.

She went through the code she wrote twice, and at this point she could only hope she made no mistakes - her eyelids were getting heavier and heavier with each minute spent over the puzzle for her friend.

With a loud yawn she placed her response together with Dipper's original letter in one envelope, closed the folds and made a mental note to mail it tomorrow morning. She then took all her many previous tries, folded them in half and tucked them in of her old schoolbook, ensuring their safety to the prying eyes of her brothers.
Earlier that day, when she started writing her response, Wendy thought that putting those few important words for Dipper would be easy, but more than two hours spent by her desk produced only a few lines, scribbled - to hers surprise - with emotions equally conflicting as in the original letter she was replying to.
Before going to sleep, Wendy pondered if she made the right choice omitting some her thoughts from the final product, hoping that maybe one day both of them might uncover them.

Meanwhile, Dipper Pines was still screaming.

A/N.: You can find this on tumblr and Ao3. Also, Fanfictionnet's formatting is awful.

And if you think Dipper has no more codes to find... Well, you are wrong.