Although the title (which translates as "Murders in Chicago") promises a gangster story, this is more of a murder mystery that kicks off with the seemingly accidental death of a construction worker, followed shortly after by that of a noted publisher (an uneasy-looking Eduardo Fajardo). What follows is a very confusing story in which the police, a police coroner (José Campos) and a vagrant (Fernando Sánchez Polack) who witnessed Fajardo's death embark on separate inquests on what actually happened. Meanwhile, June (María Luisa Rubio), who works as a secretary for the publishing company, is under pressure by a blackmailer (Antonio Jiménez Escribano) who has pictures of her in the sack with the deceased publisher.
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Roberto decides to ask for permission at the office because he suspects his wife has a lover and wants to catch her. A friend of the protagonist offers to investigate the woman with the intention of giving sufficient evidence of thedeception. However, he soon discovers that his wife knows his plans.
