While bathing in the public bathhouse his grandfather designed and built, a boy in ancient Rome is momentarily transported to a very strange place.

Rome, 128 A.D. In a golden age of bathhouse innovation, bathhouse architect Lucius tries to come up with fresh ideas that will set his designs apart.

After Consul Lepidus asks him to build an outdoor bath with a view of Mt. Vesuvius, Lucius suddenly finds himself bathing among strange-looking monkeys.

Lucius ends up in a small bathroom in a modern Japanese house and is completely fascinated by everything he finds.

Impressed by his creativity, Emperor Hadrian invites Lucius to his opulent villa and asks him to build a private bath.

Lucius works to complete a bathing area for soldiers fighting on the front lines — and not a minute too soon, as the men are in dire need of healing.

While stopping in an unwelcoming tavern during his long journey home, Lucius surfaces in a comfortable Edo-era rest stop along the Tokaido road.

On a construction site for a Roman-style spa in modern day Japan, Lucius meets a fellow bathhouse architect.

Emperor Hadrian asks Lucius to devote himself to building a large public bathhouse in the name of his son and heir to the Empire.

To undermine public support for the Emperor, some members of the Senate scheme to get rid of the man behind the popular bathhouses: Lucius.