In Chapter 29 of The Adventures of Huckleberry Finn, the King and Duke are ousted as impostors when the real heirs to the fortune (Harvey and William Wilks) arrive on a steamboat. After the stash of gold is discovered in the casket of the deceased Wilks, Huck and Jim seize their chance for escape and make off with the raft. Unfortunately, the King and Duke make their escape as well and catch up with the pair.
While the King and Duke managed to work together toward their common goal of conning people prior to being uncovered as fakes, they clearly turn on each other once they are back on the raft. They accuse each other of stealing the gold and hiding it in the coffin, and their fight becomes physical, resulting in the Duke choking the King until he falsely confesses to the theft. They also become increasingly hostile toward Huck and Jim, who can do nothing but wait until their next opportunity for escape.
The king and the duke manipulate and bully Huck, and Jim as well. Huck and Jim feel like they have no choice but to play along until they can find a chance to get out. By being nice at first, they draw Huck and Jim into their web of deception.
After Huck escapes from the mob scene at the cemetary, he and Jim shove off shore and set back down the river; however, the King and Duke catch up--unfortunately! At this point the King and Duke begin to argue w/ each other and even accuse each other of stealing the gold and then planting it in the coffin. This contrasts w/ their earlier behavior because previously they worked together in order to scam people. Also, although they were never very "nice" to Jim and Huck, now they start to be incredibly mean to the two.