In a travel show with a twist, presenter Grub Smith meets British travellers who embarked on a trip of a lifetime only to return home with some unexpected souvenirs – parasites. We join Grub on the trail of bilharzia, a nasty piece of work that can live inside your veins for years – sometimes with fatal results. He meets student Emma, returning from an idyllic summer spent in Malawi with a suspected case of the murderous worm, and Percy who was infected over twenty years ago, and has suffered the grisly consequences ever since. With the help of medical experts Grub gets the low-down on the sexual and culinary habits of the parasite and tracks it back to source, journeying to Africa to meet the people who live with it every day before finally coming face to face with the villain itself on its home turf. From rainy Sheffield to the serene shores of Lake Malawi, Grub traverses the globe on a mission to expose the parasites that have outsmarted mankind for millennia and reveals his tips on how to avoid being a victim.