In Cuba, David and Carlos uncover information that points to a possible bio-terrorist plot. The President of the U.S. immediately blames Cuba for the damaged orange groves. Jill confirms that the Korean stem cell line is contaminated with a virus, which she must prove to be harmless before her ground-breaking results can move forward. Glenn fails to respond to surgery but delivers one last message

An investigation into a cluster of suicides in the southern United States uncovers an unnatural enzyme causing sudden and severe depression. Meanwhile, David attempts to decipher the secret project of a friend who died in a car accident. In Mexico City, Bob must neutralize the Asian Brown Cloud before it rains deadly sulfuric acid. David gives Owen one more chance to clean up his act.