On a world where penicillin was never invented, Quinn is mistaken for his double, who is believed to be the cause of a massive epidemic. While he is imprisoned by a health agency, Wade shows signs of being infected and only Arturo can find the cure.

The Sliders arrive on a world that will be destroyed by an asteroid before they are due to slide. Arturo works with Bennish to develop an atom bomb to destroy the asteroid and Rembrandt gets caught up in an end of the world celebration, while Quinn and Wade confront their feelings for one another.

The Sliders arrive in the British States of America, where Arturo's double is plotting to assassinate a prince and take the throne. When the Sliders inadvertently foil the plot, they come into contact with a group of rebels trying to bring freedom to America.

The Sliders are separated on a world where the Hippie movement of the sixties is still alive and the US is at war with Australia. Wade and Rembrandt are mistaken for extraterrestrial prophets at a commune, while Quinn and Arturo race to fix a broken timer and rejoin the others.

On a world where being smart is the equivalent of being a sports star, Quinn is a popular college athlete and finds his double had underhanded dealings with gangsters. Meanwhile, Arturo discovers his late wife is alive on this world and tries for reconciliation after learning she is pressing for divorce.

Rembrandt has arrived on his dream world, where his double is as popular as Elvis, but has been dead for eight years. As Rembrandt gets to enjoy the fame he's long since wanted, an old enemy plots to make sure he disappears for good.