This is not one of the chapters your Sunday school teacher told you about, unless he or she was a twisted sadist.
Jacob's only daughter Dinah goes out to see the daughters of the land (v.1). Apparently she was between the ages of 12 and 14, and was possibly going to the tent where menstruating or recently post-partum women hung out until they were 'clean' again, which makes what follows an even greater sin in the eyes of the ancient Israelites. On the other hand, it's possible she was going out carousing with the heathen Canaanite girls, and this is a cautionary tale to good Christian girls today about the dangers of getting too close to the enemy.
Shechem, a Hivite prince, sees her and rapes her, but in what strikes me as a case of biblical fudging not all that different from Luke and Laura on The Guiding Light, he falls in love with her. He asks his father to arrange a marriage with her. The father, anxious pretend to form an alliance with Jacob, but really to gain control of his land and livestock, goes to find him.
Jacob, meanwhile, hears about the incident and tells his sons about it. They're angry, but not for their sister, for their own pride, so they're in no mood to make deals when Hamor the king shows up to ask for Dinah, and with their other daughters, in a trade alliance. Shechem asks for their forgiveness and says he'll pay any price.
Jacob's boys decide to lie and tell the Hivites they can't agree unless they get circumcised, but if they do, no problem. Hamor and Shechem are happy with the deal and they go to tell their people about the deal and find a mohel (circumcisor). So they all get circumcised and while they're still recovering Simeon and Levi come along and kill them all and take Dinah home with them. The others get in on the act and take all the livestock, the money, the wives and the kids.
Jacob tells them this won't be good, as their numbers are smaller than those of the Canaanites and Perizzites, who will now attack, but Simeon and Levi ask if they should have just let them treat their sister that way. What we never do find out is how Dinah feels about all of this, because we will find out in Deuteronomy that non-virgins cannot marry, even in cases of rape, so basically she's going to end up an unmarried girl in her father's house, then when he dies, she'll get passed on to one of her brothers and probably treated like a servant.