The play opens in a futuristic luxury palace where the wealthy elite, including the global ruler Lumley-Gotham, his family, and various societal figures, gather as a bomb threat looms. Billy Kingdon, an engineer disguised as an airplane captain, infiltrates the party to rescue his former lover, Helena, who is trapped in a loveless marriage with State Secretary Granville. As the guests indulge in trivial chatter, a catastrophic global event caused by a dangerous experimental element called radiumite suddenly destroys all other life on Earth, leaving only the characters inside the high-tech palace alive.
In the second act, the survivors realize they are the sole remaining humans on a desolate planet. The old social hierarchies instantly collapse as money, privilege, and class distinctions lose all meaning. The former servants and lower classes, represented by the butler Tuttle, rebel and refuse to obey their former masters. Meanwhile, Billy and Helena assert their independence, rejecting the old societal rules and deciding to forge a life together based on mutual love and cooperation rather than legalistic marriage contracts.
As months pass in the third act, the former elites struggle with basic survival tasks, such as cooking, gathering firewood, and manual labor, which exposes their absolute helplessness. Despite their initial resistance and adherence to old habits, they are forced to adapt to the new reality where everyone must work to survive. Debates arise over personal freedom, marriage laws, and whether to forgive past tyrannies, particularly when Granville reappears after months of hiding from a violent feud with Tuttle.
In the final act, set a year later on a peaceful country estate, the former elites have successfully transformed into a cooperative community of laborers and equals. They celebrate May Day, the anniversary of their new republic, valuing labor and mutual aid over inherited wealth and power. With a new generation born into freedom, the characters reflect on the foolishness of their old world and embrace a sustainable, egalitarian future where humanity lives in harmony without masters or slaves.
