Antonio's (Jon Seda) son was kidnapped and he has a feeling the Columbian drug gang is to blame. Pulpo (guest star Arturo Del Puerto), the Columbian gang leader, is being held in jail and suggests his release may trigger the release of Diego (guest star Zach Garcia). During the investigation, Halstead (Jesse Lee Soffer) learns some new information about Lindsay (Sophia Bush). Voight (Jason Beghe) offers Antonio a new approach to get information on Diego's whereabouts.