6:45 PM PST
After Doc, the twins, and Einstein had boarded the DeLorean - Doc then inputted October 26, 1985 9:00 PM into the time panel. Then Calvin noticed something a bit off about the time panel.
'Doc! Doc!' shouted Calvin. 'Quick! Look at the Last Time Departed panel!'
'Wha-what?' asked Doc, then he took a close look at the time panel - which read November 12, 1955 6:38 PM. 'Great Scott! This can't be right at all. We didn't come here from 1955.'
'Exactly,' said Calvin. Then Calvin pulled up some items that were next to him. It was a bag with a receipt in it, for a sports almanac - and there was also the top of Biff's cane.
'Great Scott!' gasped Doc. 'Biff must been listening to us.'
'That son of a bitch stole my idea!' Marty cried out.
'Uh, well, anyway,' suggested Doc, 'I suppose we'd better head back to 1955 - and take the almanac away from Biff.'
'Right,' agreed Marty. 'I mean, I am most decidedly not curious to see what the world would be like with super-rich Biff in it.'
'I'm sure it would be a living nightmare,' agreed Calvin.
'Well, 6:30 PM on November 12, 1955 should be early enough to arrive,' suggested Doc.
'Say, can't we just prevent Old Biff from giving his younger self the almanac?' asked Marty.
'No,' said Doc, 'you're not thinking fourth dimensionally. You must let Old Biff believe that he's succeeded - so that he'll leave 1955, and return the DeLorean back to the future. Otherwise, we run the risk of creating a time paradox, which can unravel the fabric of the time-space continuum - and possibly destroy the universe.'
'Oh, yeah, right,' stammered Marty. 'There's one problem, though. There would be another me running around. That is the night of The Enchantment Under the Sea Dance, after all.'
'You will have to be extremely careful to not let your younger self see you,' explained Doc. Then, with a sigh, Doc added, 'Unbelievable, that old Biff could have chosen that particular date. It could mean that, that point in time inherently contains some sort of cosmic significance. Almost as if it were the junction point for the entire space-time continuum. On the other hand, it could just be an amazing coincidence.'
'Okay, Doc,' said Calvin, with a sigh. 'Can you explain to me now why you only invited Marty to check out the time machine?'
'Fine, I guess now is a good time to tell you,' explained Doc. 'You see, when Marty went back to visit 1955, he went to visit my younger self - so that he could get back to the future. So, fourth-dimensionally speaking, I have met Marty many years before either of you have met me. Do you understand?'
'No, I'm all confused,' said Calvin, sighing. 'Please explain.'
'Okay, first of all, Cal - you need to be thinking fourth dimensionally, in order for this to make any sense to you,' explained Doc.
'I think I get what you're saying,' Calvin said. 'Go on.'
'Okay, when Marty had gone back to 1955, he went to seek help from my younger self - because he had no plutonium to return to the future,' explained Doc. 'So, from my point-of-view, I first met Marty - long before either of you were even born.'
'I think I understand, somewhat,' said Calvin. 'So is this sort of a chicken-and-egg scenario?'
'From my standpoint, yes - from Marty's standpoint, no,' answered Doc.
'Okay, now you lost me,' said Calvin, with a sigh.
'How do I explain this to you?' asked Doc, with a sigh. 'Okay, remember how this morning, Marty didn't remember who you were?'
'What a minute!' exclaimed Calvin. 'Do you mean to say that this Marty came from an alternate reality? Have I lost my twin?'
'Calvin,' Marty chimed in, 'I'm now starting to have memories of growing up with you. I'm starting to have two sets of childhood memories. Come to think of it, I don't even remember having problems with being called 'chicken' from the original timeline that I came from.' Then, turning to Doc, Marty added, 'How am I going to keep two sets of memories straight?'
'Just give it time, Marty,' said Doc. 'You'll get used to it, I'm sure.'
'Well, that's a relief,' sighed Calvin. 'I was so worried that I might have lost my twin forever! So, Marty, I didn't exist in the timeline that you came from?'
'Unfortunately, no,' answered Marty, with a sigh. 'I'm also happy to start having memories of growing up with you - and us being very best friends. Although, I do remember how you were initially jealous of my relationship with Jennifer.'
'Goodness! You remember that, now?' asked Calvin. 'I mean, I'm happy that your memories are coming back - but this was such an embarrassing time for me. I guess I was so worried that you would be so busy with Jennifer - that you wouldn't have time for me anymore.'
'Yeah, well, that's in the past, now,' Marty said, with a sigh.
'So, Doc,' continued Calvin, 'what were you saying now - about why I wasn't invited along for the revelation of your new project.'
'Okay, I guess I should cut to the chase,' said Doc. 'Because Marty was already in 1955, but you weren't - it would have created a time paradox to have both of you return to 1955. You see, I didn't exactly let Marty go back to 1955. It's just that yesterday also happened to be the same night that the Libyan Nationalists, who I had made a bargain with to steal plutonium for me, had found me - and tried to shoot me dead. So I had to pretend that I was dead, so that Marty would run away from the Libyans in the DeLorean - and return to 1955. That is when the Marty from the old timeline had merged with the Marty of this timeline.'
'What is this about making a bargain with Libyan Nationalists?' asked Calvin, confused. 'Aren't they a terrorist group?'
'Well, yeah, they are,' Doc replied, blushing a bit, 'and I don't quite understand why the me of the old timeline would actually do such a thing. The only reason why I did was for the events to take place in the same way as they did in the old timeline. Marty had brought back a video from the old timeline - so I had watched my older self from the future. Also, Marty had written me a note, warning about the Lybian Nationalists. Initially, I tore up the note - worrying that knowing too much about my future would create a time paradox. I eventually relented, and taped the letter back together. I was so glad that I did. I mean, poor Marty! He had already lost me once - and he was worried that he would lose me again. When I heard Marty crying, thinking that I was dead, my heart really ached for him. I feel so bad about putting him through that trauma. I should have sensed his desperation back in 1955 - but I was too stubborn. I guess I didn't realize just how close Marty was to my future self.'
Marty was blinking back tears, as he remembered how grief-stricken he was when Doc tore up the letter, and how he couldn't catch Doc in time. If Doc never did read the letter, then... A tear slid down Marty's cheek.
'Awww, Marty,' sighed Doc, as he dabbed at the tear that slid down Marty's cheek with his index finger. 'I am so sorry! I wish I wasn't so stubborn. I wish I never tore up the letter!'
'Well,' said Marty, with a sigh, 'I'm so happy that you finally did decide to tape the letter together. There's no telling what I would have done, if you had turned up dead.'
'Okay, I guess I understand now, Doc,' said Calvin. 'Thanks for explaining.'
'Well, boys, shall we head back to 1955, now?' asked Doc.
'Sure,' replied Marty and Calvin, simultaneously.
The time display suddenly changed to JAN 01 1885 12:00 AM.
'Damn, gotta fix that thing!' groaned Doc as he banged it, and it changed back to NOV 12 1955 06:00 AM. 'All right, time circuits on. Marty, Calvin, Einie - brace yourselves for temporal displacement.'
Then Doc began to pilot the DeLorean onto the skyway, until he got up to 88 miles per hour - then, just as they were about to pass a floating sign, the DeLorean broke the time barrier.