Yummy is an orgy of blood, violence and fun in which a young couple travel to a shabby Eastern European hospital for plastic surgery. The young woman wants a breast reduction. Her mother comes along for yet another face-lift. Wandering through an abandoned ward the boyfriend stumbles upon a young woman, gagged and strapped to an operating table; she is the result of an experimental rejuvenation treatment. He frees her, but does not realize he just caused the outbreak of a virus that will change doctors, patients and his mother-in-law into bloodthirsty zombies.

Weird yummy goo erupts from the earth and is discovered by a couple of miners. They taste it and decide to market it because it tastes so good. The American public literally eats up the new dessert sensation now known as the Stuff but, unfortunately, it takes over the brains of those who eat it, turning them into zombie-like creatures. It is up to ex-FBI agent David Rutherford and a kid named Jason to stop the spread of the mind-devouring dessert.