The CSIs investigate the murder of a neighborhood do-gooder who was known on the streets as Reverend Mike for his work trying to keep kids out of gangs. The team runs into a roadblock until an anonymous crime "tipster" comes forward with key evidence which points to a local gang, Los Craneos. But when the Craneos discovers the identity of the tipster, Horatio has to race to save her before a rigged bomb blows. After rescuing her, Horatio discovers the tipster has been working for a secretly reformed gang leader, Hector Salazar, who is trying to restore old school dignity and safety to the neighborhood. Unfortunately, he's gunned down by the Craneos, the very gang he used to lead. As Hector dies in his arms, Horatio promises to finish the job and make the streets safe again.