The CSIs are brought in to investigate a series of deaths tied in with rabies. There is no evidence of animal bites, and everyone is stumped. Catherine is bitten by one of the subjects, and has to go for the antidote as soon as possible, because rabies is fatal if not treated in the first 72 hours. The team realizes that there is an ex-coroner from Reno who now runs a tattoo parlor in Vegas who has been doing experiments on his clientele by injecting them with rabies from a certain kind of bat. The evidence is very tough to find -- and Doc Robbins and Langston get to the bottom of this highly scientific case.