While working in his basement, Quinn Mallory opens the gateway to parallel worlds. For a test run, Quinn invites co-worker Wade Welles and his teacher, Professor Arturo, along. Upon opening the vortex, Quinn uses too much power, which causes the vortex to suck them in along with Rembrandt "Crying Man" Brown, who happened to be driving by Quinn's house. The four arrive on a world that experienced an ecological disaster and will have to survive until the timer hits zero.

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.

After separating from Ryan and Henry the dog, the Sliders make a rough landing that reopens Quinn's bullet wound. On this world of mysticism and superstition, a witch doctor heals Quinn and has brains on the mind when they can't pay the bill. On the run from bounty hunters, the Sliders only hope is the mysterious Sorcerer, a man who could possibly get them home.