Col. Henry Brooks, with the Defense Advanced Research Projects Agency (DARPA), asks Hood and Rachel to investigate an experiment funded by his agency that appears to have gone horribly wrong.
Dr. Bruce Nesic is doing drug research on chimpanzees, that might one day be used to improve the fighting abilities of US Soldiers at war. Unfortunately, one of the chimps appears to have attacked and killed all the other chimps, as well as severely injuring one of the veterinarians on the research team. When the violent chimp disappears, then is found dead near the body of an animal control worker who had been searching for him, Hood figures out the scene has been staged. Further investigation into Nesic's data, leads Hood to the fact that Nesic has also run a human trial on the drug therapy and that the violent soldier has gone AWOL. Hood and Rachel track down the missing soldier and find a way to talk him down from his now-instinctive violent response.