When a strange fly bites one of the Smurfs, a full-on epidemic develops in the Smurf village! After being bit, a Smurf turns purple, his vocabulary is reduced to one word (GNAP!), and he goes berserk! The purple Smurf runs amok around the Smurf Village biting other Smurfs on the tail, causing them to turn purple and act crazy too! Soon there are more purple Smurfs than blue Smurfs in the village. It's up to Papa Smurf to find a cure and save Smurf Village before all of the Smurfs lose their minds for good!