The Levite and his concubine (could have been a lesser wife since polygamy was allowed and her father supported the relationship) were staying with an elderly man in Gibeah. The men of the town came to the house and demanded the old man give them his male guests (the Levite and his servant) to sexually abuse. He wouldn't but tossed out his virgin daughter and the concubine instead. The Levite sends parts of his concubine to the tribes to shake them up out of their moral lassitude. (But let's not ignore the fact he himself did this despicable, reprehensible thing himself in allowing a woman in his care to be abused like this.)

I'll see your incest and raise you dismemberment of a corpse. Young Levite tosses his concubine out into the street where she gets gang raped and left to die, which she does the next morning. He cuts her body into 12 pieces and sends one piece to each of the tribes.