Jesse and her partner Liam respond to a suspected anthrax attack in the underground railway, and are soon on the trail of the suspected attacker. Can it really be Walter Preston, the mysterious old man who grows herbs on his balcony and is kind to children?
Jesse thinks not, but follows him just the same, only to see him in a meeting with her controller, Director Granger.
When Preston collapses suddenly after his meeting, Jesse begins to suspect that Granger's involvement in this affair may be much more sinister. What is Director Granger's relationship to Walter Preston? And what are C2 and Nimbus going to do with their knowledge of germ warfare?