2 Samuel 16 - As David flees from his son's challenge to his throne, he is met with several disappointments. First, Ziba, the servant to Mephibosheth, the son of Saul who David was being kind to, said that Mephibosheth was going to try to get the throne back for himself. (Later, we'll see that Ziba was laying). This news must have hurt David to think that this man he had sought to help would turn against him. Then, David faces Shimei, a man from Saul's family, who came out to curse David as he fled. Though David's men wanted to "take his head off" David refused and suggested that if God wanted Shimei to curse David, so be it! David felt his own son was hurting him, so he wouldn't worry about what this man had to say.
On a side-note I've often chuckled when I read that Shimei "threw stones at David." Who would you NOT want to get into a rock fight with more than David?! Remember how he killed Goliath - one stone!
Meanwhile Absalom gets advice from Ahithophel, to have sex relations with David's 10 concubines. This would be Ahithophel's way of getting back at David. Why do I mention Ahithophel's revenge? It can be demonstrated that he was Bathsheba's grandfather.
2 Samuel 17 - Ahithophel gave Absalom further advice on how to kill David. It was a workable plan, according to verse 14. But David's friend, Hushai, stepped in with an alternate plan that would eventually work to David's favor. Absalom listened to Hushai which caused Ahithophel to feel the rejection and he would end up hanging himself. A lot of sadness in the life of David has come about because of his terrible sin with Bathsheba.
2 Samuel 18 - David's men were well-trained and they mounted a defense against Absalom which brought ultimate victory for David. But, against his wishes, his men, namely Joab and his associates, killed Absalom. This brought heart-wrenching grief to David when he heard and he cried out, "O Absalom, my son, my son." Perhaps David thought he could forgive his son and change him, but that was not to be.