The player character awakes after being rescued from floating down the Tiber by a young woman named Karen. She asks them to look for another saved individual, Al Worth, who had disappeared whilst investigating ancient Roman ruins of an underground city full of golden statues resembling ordinary people. The player discovers Al, who had committed
suicide by hanging, with a note beside him remarking that the player ought to die rather than engage with a strange portal hidden in the ruins. The portal takes the player back in time to a living version of the city, where they meet a farmer named Galerius who takes them to the
magistrate Sentius. Sentius explains that the city, which comprises less than two dozen people, is bound by a "Golden Rule" where if even one commits a sin, the whole city is doomed to be turned into golden statues, many of which are littered around the city from prior communities which failed to live up to the Golden Rule. Sentius, however, is aware that the Golden Rule will be broken later that day and has prepared a ritual to
Proserpina to create a portal which takes the player back to the start of the day if the Golden Rule is broken. The only way for the player to escape is to create a
time paradox, where if the Golden Rule is never broken, Sentius will have no reason to perform the ritual and the player will return to their own time. The Forgotten City has four different endings. The first ending consists of shooting Sentius with either a
pistol brought from the present or a golden bow with the capacity to turn anything it hits into gold. This creates a time paradox as Sentius is unable to complete the ritual, but the player and Al are trapped in the ruins of the city and ultimately perish. The second and third endings consist of discovering Sentius' lost daughter, Sentilla, locked in a cistern above the city, connected to a hidden aqueduct with the opportunity to escape. As escape would violate the Golden Rule, Sentius himself imprisoned Sentilla to prevent her escape. Upon freeing Sentilla, Sentius reveals that he preserved all his memories from each loop and did not intend for the protagonist to ever prevent the Golden Rule from being violated, commenting on how Al spent thousands of days trying to do so before ultimately committing suicide. Sentius' motivation, rather, is to use the ritual and the player's time loop as a way to attain
immortality. Sentilla then
sets Sentius on fire, violating the Golden Rule and causing a time paradox, before escaping: either alone in the second ending or with others from the community in the third ending. The player and Al then return to the present world of the living. The fourth ending, referred to by the game as the "
Canon Ending," requires the player to discuss how various individuals came to arrive at the community with the
Vestal Virgin Equitea. Here, the player learns that they are actually in the
Underworld: the river at the start of the game was not the Tiber but the
Styx, and Karen's name was merely a different pronunciation of the ferryman
Charon. Equitea tasks the player with collecting four plaques necessary to unlock the Grand Temple at the top of the community. These four plaques represent four communities from the history of the city—Romans,
Greeks,
Egyptians, and
Sumerians—who gradually built cities on top of each other that hid the existence of the prior cultures. Upon unlocking the Grand Temple, the player meets
Pluto, a member of a
superintelligent alien race who arrived thousands of years ago to guide humanity and were deemed to be gods due to their advanced technology. Most of the aliens deemed humanity to be naturally violent and sinful, electing to return to their
utopian homeworld. Another alien, Proserpina, saw potential in mankind and turned herself human, leading Pluto to leave her in
suspension. Proserpina's father,
Jupiter, forbid her from returning as no human was permitted to go to their homeworld. In response, Pluto made a wager with Jupiter that humans were capable of living for a full year without sin, leading to the creation of the city and the Golden Rule itself. Pluto minted one thousand
silver coins which would bring those who held them in death to come to the city in the
afterlife. The community the player finds themself in is the last one that could possibly succeed, as there are only two coins remaining by the Romans' time: those which would be later discovered by Al and the player, causing both of them to arrive at the city. The protagonist succeeds in either convincing Pluto that the Golden Rule's enforcement leads to sin itself, or intimidating him using the golden bow, ultimately leading to the suspension of the rule and the creation of a time paradox. Pluto sends all members of the community, as well as Al and the player, back to the land of the living, but to the present rather than during the time of the Romans. The only exception is Sentius, who is left as the sole golden statue in the sealed-off underground city for his crimes. The
epilogue consists of the player meeting all living individuals from the city in a present-day museum, as well as Proserpina, who had been the voice in the statues whispering to the player throughout the game. The game ends by revealing that all the statues, not just the people alive during the final city, had been brought back to mortal form and transported to the present. == Development ==