Dipper read. It said "One letter forward." He had no idea what it meant then he tried something out. He got the letters in the message and used the letters before them.
So VDMCX HR Z VDQDVNKE actually meant WENDY IS A WEREWOLF. Dipper was shocked. He thought he was just dreaming. He slapped himself to make sure he wasn't dreaming. Bud sadly, he wasn't dreaming.
Dipper took out his book and turned to the page about werewolves. It said "Werewolves are the most deadliest creatures that have ever existed. They often disguise themselves as human beings, but whenever there is a full moon, their appearance's change. Just one scratch from them can lead to death. Their weakness is unknown…" The rest of the page was just pictures.
Dipper quickly closed everything and cleaned up, then left. Dipper was speechless. He ran back to the Mystery Shack to show this to Gruncle Stan and Mabel. When he got in, he asked for everyone to come downstairs. Once they were both there, he showed the letter and the secret message. He yelled "Can you believe this!?"
Mabel and Gruncle Stan laughed. They said "Dipper, you really got us this time!" Dipper walked out as they were laughing.
Dipper went to the police (A.K.A Sheriff Blubs and Deputy Derlin) to show them the letter and the message. They were shocked. Sheriff Blubs asked "Where did you find this?" Dipper said "In the bottom of a cookie jar, and I want to know if you guys know who wrote this and what it means."
They said to Dipper "This was written by a man named Timothy Smith. He was known for the country's greatest detective. Then one day, he went a house and never came back. The only clue we have of where he disappeared is this strand of hair. Apparently orange." Dipper whispered to himself "Wendy's house." Then Dipper said "Guys, follow me. I think I know where he disappeared."
They then said "Whoa whoa whoa. The last time we followed you, we got the wrong suspect."
Dipper said "Just trust me this time. I know what I'm doing."