Peeling an onion can get dicey.
At first we meet the chiropody man, a kind and gentle soul, but through a wacky ride through time he suffers peculiar anomalies: psychologically, physically, and the acceleration of the aging process. After all, time travel is rough for the uninitiated. Without modification of his DNA, a process developed in the future via genetic modification through nanoparticles: tracked, traced, and healed by orbiting satellites.
After the first portals were mapped out, by the 2070s anyone with the means could have a weekend in any era. Dinner in Ancient Rome? No problem. However, the future has to keep tabs on time travelers, and make sure they don't go astray.
Time travel "by accident" has consequences. There are powers and forces in the universe that cannot allow for altering the past. A mysterious country doctor, from a country, yet to be discovered, and a crew of characters selected from other times come together, to take this voyage to restore the proscribed dynamics set forth. Intentions, obstacles, a clash of artificial intelligence, greed, authentic ignorance, temporal mercenaries, and a little bit of luck, things on Earth can stay the course.