Hest's right-hand man was Sedric Meldar, a friend of Alise's from her childhood. He served as Hest's secretary, but also kept many of his secrets. Sedric was sent with Alise into the Rain Wilds so that she may see the dragons before they headed upriver to find the elusive and lost Elderling city of Kelsingra. But he had a secondary purpose to the journey that led him down a dark path...
And Leftrin, captain to the liveship Tarman, is tied to the dragons in his own way. In the first book, he found a wizardwood log - a dragon cocoon - washed far into the Rain Wilds. He and a hand-picked crew took it and worked the magical "wood" into his liveship to make it even more powerful than before. When the Tarman is contracted to help guide the keepers and dragons upriver, Leftrin becomes entangled with Alise and Sedric and falls in love with the Bingtown woman.
Dragon Haven continues the journey of the Tarman, keepers, and dragons upriver to find the mythical Elderling city of Kelsingra. Nobody knows if the place is real or imagined by the dragons, but they continue searching for clues as they delve deeper into the uncharted territory of the Rain Wilds.
Along the way, the dragons, keepers, crew of the Tarman, Alise, and Sedric learn more about themselves each day of the expedition. The dangers of the acid waters and simply finding enough food and fresh water to keep everyone alive would be tough enough, but unexpected dangers force everyone to reevaluate their situations and possibly even find happiness or at least understanding as they journey on.
I don't want to spoil too much of the plot, but I will say that the end works extremely well to tie up many loose ends in a satisfying way without closing the door on future books exploring the world Hobb has created.
As I said in my review of The Dragon Keeper, this is serious, adult fantasy dealing with complex issues. I found it interesting that in the first book there was an unwelcome sexual act (Hest forcing himself on Alise on their wedding night), and in Dragon Haven we deal with almost a Lord of the Flies situation with a coed group of keepers roaming free with little or no adult supervision. This leads to some sexual experimentation by a few characters and an incident of voyeurism that leads to conflict among the keepers throughout the story.