Horror Show? Such as genetically engineer E. coli bacterium to produce LSD, and then accidentally release them into the environment (city water supply) so that everyone coming into contact with the infected body of water develops their own LSD-producing bacterial culture in their gastrointestinal system - everyone goes boinkers, and the source of the LSD found in the bloodstream of all the affected people cannot be determined until it is to late and the bacterial strain has spread to a large portion of the population. It would also be impossible to eradicate it, as the strain can not be specifically targeted by antibiotics, and killing off the entire E. coli population in the world is out of the question, as that would do even more harm than good.
Ok, that's the synopsis. Where is Stephen King when you need him to write a complete movie script?
The sequel is pretty obvious - In "Acid Bugs II" the E. coli strain once again escapes into the environment, and this time not restricted to E. coli, the gene plasmids transfects other single cell organisms just like antibiotic resistance is carried across different species. Finally, when introduced into blue-green algae, the entire animal population of the world is at risk of going insane, as the LSD concentration in the oceans rise exponentially, as the new genes bring such an advantage to the plankton as all species which usually eat it gradually gets more and more incoherent in their actions until they cannot feed themselves - will the earth be covered in a thick slime layer of blue-green algae floating on an ocean which has turned into an aqueous solution of LSD, or will our heros save the world in time?
Acid Bugs III - coming soon to a theater near you. This time the LSD-producing genes has mutated to take advantage of the chlorinated hydrocarbons from the pollution of the environment, synthesizing a halogenated LSD analog 100 times as potent as the original, and which is not biodegradable...