- "He [the man] reached inside his trenchcoat. Marty took a step back. Did the guy have a gun after all? / He pulled out a long thin envelope. / 'A letter,' Trenchcoat announced. / 'A letter?' Marty asked, taking a closer look at what the other held in his hand. It was an old, yellowed envelope, with a red wax seal holding it closed."
- —From Back to the Future Part II by Craig Shaw Gardner (quote, page 212)
- Western Union man: "I got something for you... a letter."
- Marty: "A letter for me? That's impossible!"
- — After the DeLorean was struck by lightning
- "Great Scott! / This was astounding. Doc Brown had to admit it — even with his advanced scientific brain, it had taken him a moment to grasp an idea of this magnitude. / But the letter was certainly in his handwriting. And, if his handwriting actually what he thought he saw in his first cursory glance, why the implications were enormous! / At the very least, it was very exciting. And an obvious subject for further research. After a hasty breakfast, Doc and Marty had adjourned to the laboratory he kept in his garage — Doc did like to keep his scientific endeavors separate from his home life, after all. It was important to keep a proper balance in these things. Now, however, that he was in the proper surroundings, he felt fully justified in pacing about as he read the letter aloud."
- —From Back to the Future Part III by Craig Shaw Gardner (quote, page 11)
After settling down as a blacksmith, on September 1, 1885, Doc gave the letter to Western Union with the explicit instructions that it be delivered on the highway in front of the future Lyon Estates to a person responding to the name of "Marty McFly" on November 12, 1955, the same place and time as when he disappeared when lightning struck the DeLorean time machine.
Western Union held the letter for over 70 years and many in the department made bets as to whether this "Marty" would actually show up at that very location and at that very time. The delivery man had bet against there being anyone there, but he was proven wrong when Marty was found standing right in the middle of the highway in the rain as he pulled up.
Marty opened the letter in the rain and realized that it was from Doc, and ecstatically jumped for joy. Marty ran back to town to find the only man that could help him at that point, the younger Doc Brown of 1955. After Doc sent the first version of Marty back to the future, the second version ran up the street from behind and took Doc by surprise. Doc fainted and Marty drove him to his mansion in his Packard.
Doc woke up to Howdy Doody starting to play on his television set and started to record the events of the night before on his reel-to-reel tape recorder, saying he could not figure out how he arrived home, unless there was an effect of temporal displacement that created temporary amnesia. Marty appeared and showed him the letter. Using a magnifying glass, Doc proceeded to read aloud the letter, and also studied the enclosed map for reaching the DeLorean hidden in the Delgado Mine.
If my calculations are correct, you will receive this letter immediately after you saw the DeLorean struck by lightning. First, let me assure you that I am alive and well. I've been living happily these past eight months in the year 1885. The lightning bolt that hit the DeLorean caused a gigawatt overload which scrambled the time circuits, activated the flux capacitor, and sent me back to 1885. The overload shorted out the time circuits and destroyed the flying circuits. Unfortunately, the car will never fly again.
I set myself up as a blacksmith as a front while I attempted to repair the damage to the time circuits. Unfortunately, this proved impossible because suitable replacement parts will not be invented until 1947. However, I've gotten quite adept at shoeing horses and fixing wagons.
I have buried the DeLorean in the abandoned Delgado Mine, adjacent to the old Boot Hill Cemetery, as shown on the enclosed map. Hopefully, it should remain undisturbed and preserved until you uncover it in 1955. Inside, you will find repair instructions. My 1955 counterpart should have no problem repairing it so that you can drive it back to the future. Once you have returned to 1985, destroy the time machine.
Do not — I repeat — do not attempt to come back here to get me. I am perfectly happy living in the fresh air and wide-open spaces, and I fear that unnecessary time travel only risks further disruption of the space-time continuum. And please take care of Einstein for me. I know that you will give him a good home. Remember to walk him twice a day, and that he only likes canned dog food. These are my wishes; please respect them and follow them.
And so Marty, I now say farewell and wish you Godspeed. You've been a good, kind, and loyal friend to me, and you've made a real difference in my life. I will always treasure our relationship and think on you with fond memories, warm feelings, and a special place in my heart.
Your friend in time,
"Doc" Emmett L. Brown.
September 1, 1885.
After reading the letter, 1955 Doc couldn't believe how he would be able to write something so beautiful and was briefly overcome with emotion. After wiping the tears from his face, Doc picked up the map to the Delgado Mine and located an area to blast through.
Inside the buried DeLorean, Marty and Doc found another envelope. Marked as such, this contained the pages of repair instructions that 1985 Doc had mentioned in the third paragraph of the letter.