They will be allowed one investigation nightly,on nights 2,3, and 4 only, since they want to destroy the town's Bio-Engineers, before they find a cure-all serum. Dr. Gene will PM me the victim that will be tested each night, and who they wish to investigate. If Dr. Gene should be eliminated early on, the remaining Evil Scientists will have to PM me individually.
The good news is if they screwed up their hit tonight... it's fairly certain they missed out on their investigation tonight, too. So they're nowhere closer than they were before trying to guess who the Bio Engineer is.