Do you know Robert Heinlein? If you don't, go read his works! If you only know Starship troopers and you don't like it, don't let that stop you, there's much better! In no particular order: Starman Jones, Citizen Of The Galaxy, Have Space Suit Will Travel and not least the whole saga about Lazarus Long whose best known example is Time Enough For Love. Personally, I discovered his works in my Harry Potter period when I was following a yahoo group called WIKTT as I searched for the reference behind a fan-art. Besides (unrelated) if you read fanfictions on this universe, there is one story I can't recommend enough : The Arithmancer and the follow up Lady Archimedes by White Squirell. (What if Hermione had never stopped learning mathematics ...) All this to say that this story is inspired by a scenario by Robert Heinlein, whose foundations are laid out in Time Enough For Love (1973) and which is executed in To Sail Beyond The Sunset (1987).
Professor Sato then shows Professor Mortimer what is going on behind the scenes, the machines embedded in the walls and the controls on the other side of them, leaving Mortimer time to gather all this information in his boiling mind.
"Oh, what is this?" Professor Mortimer notices a paper lying on the floor, bends to pick it up and sees a few words scribbled in Japanese writing.
"Ah," Sato answers. "It's a note that was pinned on this door, Mortimer. It reads, 'Do not use for ten years.' It must have fallen when we decided to use this room to store some equipment. The first time I saw it was just after we had the villa rebuilt after the fire and I respected the instructions. But the strangest thing is that it's my handwriting and I don't remember drawing these characters."
A solution is gradually taking shape in Mortimer's mind, but he still doubts; he doesn't want to prematurely transform his hope into conviction. "Are you sure that no one but you and your daughter are aware of your breakthrough?"
"Of course, my friend. I would also count you as well as all the guinea pigs, but the secret is well kept, you can be sure of it."
Slowly, Mortimer speaks the conclusion that these few words have crystallized. "You're telling me that I saw myself, that you used your procedure on me, and that I went back to the past."
Professor Sato, imperturbable, barely raises an eyebrow. "Mortimer, you were the one to tell me that you had already traveled in time."
"Yes, of course." Mortimer is already deep in thought. Would it be feasible? The machine invented by Miloch has disappeared, destroyed in the Bove's explosion. Mortimer has only bits and pieces of information to rely on. A few years ago he researched some of the theory behind the chronoscaphe and he had seen the inside of the time selector circuits at the time, but it would take months, if not years, to recreate all that! At his age, he wonders if he still has this time, but if Sato's invention works and can win him this delay!
Yes. That must be the solution. If it was neither an android nor a clone, it must be himself that he saw. Already he draws up plans, begins to mentally take notes on the phases to achieve. He will have to draw a flowchart in order not to forget any key step**.
But then Professor Mimiko Sato comes to join them to explain the more medical details and Mortimer lets himself be guided by his hosts whose explanations only reinforce a resolution he has already taken.
* See The Time Trap.
** About temporal journeys : "it's a tiny bit complicated. People usually need a flowchart." Dr. Who (The Husbands of River Song)