This paper focuses on the case of an individual diagnosed with mixed personality disorder (antisocial and borderline). He is a 34-year-old male, currently held in a maximum-security prison in Romania. His pathological pathway toward disharmony began in childhood and adolescence, comprising a delinquent behaviour associated to and exacerbated by the use of alcohol and psychoactive substances. Criminal behaviour becomes fluent and unstoppable: it leads to multiple aggravated assaults and property destructions. Overall, he committed 41 offences; eventually, it led to the first murder, for which he was sentenced to 20 years in prison. While in prison for serving his first sentence, he committed two other murders. The clinical and criminal picture is completed by psychoactive substance abuse, nonadherence to treatment, and ignorance of professional recommendations.