19 - A Levite has a concubine! She is unfaithful to him. Retreiving her, they stay in Gibeah of Benjamin, where the inhabitants brutally violate her (think Sodom) until she dies. The Levite informs all Israel of this, brutally.
20-21 - Israel goes to war against Benjamin and all but wipes them out. Israel figures out a way to restore the tribe, providing wives for Benjamites.