As Phineas continued to work on the computer, entering the various binary codes Titor had instructed him to enter, Ferb watched. After a moment, Ferb held up his hand looking at it.
Isabella blinked, looking to Ferb. "Ferb, what is it?" she asked.
"I was just thinking what the future would be like, if we grew an extra finger."
"Five fingers?" asked Phineas smiling. "That'd be pretty insane."
"You know," Isabella said, "readers are probably going to leave comments that this joke was already used in the Simpsons or something."
"What comments?" Phineas asked.
They all laughed.
"Alright," said Phineas, wiping his head with the back of his hand and standing up, "everything's been programmed, all of the binary set." Then he looked to Candace. "What next Candace?"
Candace shrugged. "Well, he said in the note just to wait for him to call," she said, shrugging. Just as she said that, her phone rang.
"Here he is," said Phineas nervously, glancing to Ferb and Isabella before looking back to Candace. "You uh, want me to answer it?"
Candace held the phone to her angrily. "No!" she snapped, "it's my phone, I'll do the answering." Then, slowly, she flipped it open and held it to her ear. "Um, hello?" she asked nervously.
There was a pause as they all looked at Candace.
"Look bud, it's MY phone," said Candace, "I'll do the... alright fine." Then she handed the phone to Phineas. "Guy's pretty persistent."
Phineas rolled his eyes as he took the phone, then said into it, "Hey cuz."
"Second cousins," the voice Phineas knew as Titor's replied. "Have you finished the programming yet?"
"It was difficult," Phineas replied, looking down at the old computer, "but we got it."
"Alright," Titor said. "Listen to me very carefully. You canno-..."
"Huh?" asked Phineas, then looked down at the phone. "Looks like the signal cut out. I think he was about to say cannot. We cannot, something."
Ferb blinked. Then pointed.
All of them turned towards the direction that Ferb pointed. Coming up the driveway was a large white van. It was unmarked, a man driving and a woman in the passenger seat. Both had on well tailored suits.
The van pulled up and stopped, both of them getting out. "Excuse me," said the man, walking up to the gate and looking down at the kids, the woman next to him also looking at them. "Is this the Flynn-Fletcher residence?"
Candace grabbed her phone from Phineas. "Who's asking?" she asked, her eyes narrowed.
The man and woman looked at each other, then turned back to face the group. "We're from a group called the European Organization for Nuclear Research. Our labs are based in Switzerland but, we were told that someone here in the Tri State area, going by your name, had in their possession an IBM 5100 which had been programmed to fix a Y2K 2015 problem."
Phineas leaned over and whispered to Ferb, "Hey Ferb, we were at an award ceremony in Switzerland when we went into the future, remember?"
Ferb nodded quickly, looking back.
Phineas faced the two adults. "We have it," he said. "Were you meant to fix that problem using this computer?"
The man nodded quickly. "Yes," he said, "we must get it to the proper authorities quickly. Is this the IBM 5100?" Then he nodded to the computer sitting on the lawn.
"Why yes," Phineas said, "yes it is." Then he went over and picked up the old computer with some effort, and carried it over to the adults. "Here you go," he mumbled, then let out a phew as the man tool it carefully out of Phineas' arms. "Why would you need an old computer to do that, anyway? Putting in the program specs was a lot harder than using just a normal computer."
The man smiled gently. "In order to fix all of the mainframes," he said, "we couldn't use a current computer. We had to go back and try to find a computer that was used to create the original systems that the current OS's are based on."
"OS?" Isabella asked curiously.
"Operating System," Phineas said to her. "It's what we use to operate computers. Y'know, like Doors 2000."
"Oh," Isabella said, smiling as she understood.
The man nodded. "Well, we'd better get this back to Geneva kids. You've done great here."
The two went back to their van, and drove off. That's when Phineas noticed the odd logo on the side of the van, interconnected circles with the word CERN printed in the center.
"Huh," Phineas said curiously, his eyes following the van as it went down the street. "CERN. Why is that name so familiar?"
Ferb tapped his brother on the shoulder, then made a circular movement with his hands.
"Oh, yeah," said Phineas, "the LHC!"
"The LH what?" Candace asked.
"The Large Hadron Collider," Phineas said. "It's designed to collide particle beams into each other so that we can research the very fabric of existence. They even say it could..." then Phineas' eyes widened, his mouth dropped open and he stared at Ferb. Ferb only stared back.
"Phineas," Isabella chimed in looking nervous, "they say it could what?"
Phineas slowly looked to Isabella. "Lead to time travel," he said.
THE FUTURE: YEAR 2015
Phineas and Ferb both rested on their couch, enjoying the warm July day. They both were in high school now but still had summers to enjoy while Candace was in college. Normally the older Candace would still be there, only she was at home during her school's summer break.
No longer did she worry about busting Phineas and Ferb for whatever crazy scheme they may be up to. Candace simply laid on her back on her bed in her room, lazily talking to Stacy on her phone when the signal was abruptly cut off. "Huh?" Candace asked, sounding annoyed.
In the living room, Linda Flynn-Fletcher walked in handing over an envelope to Phineas. "Here you go boys," she said, "looks like you got mail." Just as she finished saying that, the lights went off, as did the television. "Oh dangit," she mumbled, "your dad must be using the power tools again. Probably flipped a breaker." Then she headed to the basement.
Phineas looked at Ferb curiously who only looked back with a blank stare on his face.
Phineas opened the letter. It was hand written in very neat penmanship. Phineas looked to who the letter was from. It made him jump slightly in his chair. "It's from Titor!" he exclaimed. Then he held the piece of paper away from him as if shocked by it, but decided to read it aloud anyway.
"Dear Phineas and Ferb," Phineas read.
Somewhere in the world, alarms started going off. Panicked men started screaming in Russian as missile bay doors opened.
"I'm sorry to say," Phineas continued, "that what I meant to tell you that day when we talked was that you cannot give the computer to CERN, that they will come looking for it. They..." Phineas gulped. "They will only use your programming to solve the problem for themselves, so that the LHC can go on as planned. They do not care about the rest of the world."
Somewhere in the world, a missile stood at the ready to launch. More men screamed at each other in Russian, but none of them could stop what it was about to do.
"I'm sorry to say that CERN has used it to save the LHC but nothing else. The failure of mainframes worldwide will still happen, as will..." Phineas' eyes swelled with tears, "as will the nuclear war that I tried to prevent." Phineas was shaking now and Ferb just gently rested a hand on his shoulder.
Phineas hugged his brother, then went back to reading. "Take comfort in knowing this: The Tri-State area will not be hit and will survive the attack, that the LHC will lead to time travel being developed, and that because of CERN's mainframes being fixed, the rest of the world will be able to get back online, once the nuclear war has completely ended. You will go through hard times, Phineas, but be brave cousin. You will not have to go it alone. You have your family, you have your friends, and you have one other who will make himself known to you soon. By the time you read this, I will be back in my own time, 2036. Some things we cannot change, Phineas. Some things time just will not allow us to change. Even if you have been to the future, it was a future that could never be as it was a future that would happen without my travelling back in time, before I changed your worldline just by being here, before the threat of 2015 was ever accounted for. I either changed your future, or I fixed it, I can't say. Either way I'm sorry. The future is blank, Phineas. We write it, and some things were just not meant to be changed. Good luck, Phineas and Ferb. -John Titor."
Phineas once more fell into his brother's arms, crying, the letter falling to the ground.
Once the piece of paper gently made contact with the floor, the missile, along with hundreds and hundreds of other warheads, suddenly launched from Russia.
Somewhere in a NATO command center, the announcement that Russian nuclear warheads were flying towards various parts of the world came through, and plans for retaliation began.
"You're on your own now, Agent P.," Monogram said to Perry through his wrist communicator after hearing Phineas read the letter. "I suppose we all are now. We will try to continue OWCA, but... it will be a very different world now. Consider the Flynn-Fletcher family your permanent host family now, Agent P. Your mission is to protect them and comfort them, get them through this. I will keep in touch."
Perry smiled weakly, his eyes filling tears as he stood and saluted. Then he put on his hat, and walked forward, both Phineas and Ferb looking down at him curiously.