When a girl, Lauren, brought into the ER pale and unconscious, dies from complete organ failure, Alexx Woods believes she was murdered from an unknown poison. The main suspect is her boyfriend, Ethan, who was planning on proposing to her. Horatio and the team test everything in her apartment for any sort of poison. When the boyfriend collapses during Delko's questioning, they discover Lauren was poisoned with a deadly strain of E-coli. The team investigates the restaurant where Ethan and Lauren last ate but are directed to the farm where the produce comes from, as E-coli starts with the grower. Ryan, Jesse and Walter get resistance from the farm but manage to test the crops and come up with nothing. They investigate other methods the strain could have infected the crops and discover everything is controlled by a larger corporation, Bixby Organic Foods. They secretly go back and test the irrigation system and discover the water tests positive for E-coli as it goes right through a manure invested cattle field. They discover the corn that's feeding the cows is a perfect breeding ground for E-coli but when Alexx tells them that Ethan doesn't have an E-coli infection they have to dig deeper as to what the source is. Bixby was growing genetically engineered corn to make easier to digest and Ethan had eaten some of that corn, showing symptoms of botulism and succumbs to it. Horatio confronts the CEO of Bixby but he claims a few deaths is worth feeding an entire nation. Although Horatio can't press charges, he has enough evidence for Ethan's family to file a law suit. Delko is overwhelmed by not being able to save either Lauren or Ethan and leaves the team.