This is a fantastic series....you GOT to read the first 3 books to get this one completely.
It expounds on the building friendship of Alfred and Haplo- mortal enemies-and the breakdown in their hatred for each other's people. Light is shone on the history and mystery of this ancient hatred.
This book made me instantly open up book 5 as soon as i finished it's last page!
After the four worlds Alfred has at last found his people on Chelstra, the realm of sea. But his travels have taught him to be cautious... and Alfred soon realizes his caution is justified, even among his own kind. The one person Alfred can trust is, strangely, Haplo the Patryn. But Haplo's lord has decreed all Sartan to be the enemy, and Haplo dares not go against his lord. Now the companions have arrived in a land where humans, elves, and dwarves have learned to live in peace. Unaware of an even greater threat to all the realms, it is Sartan and Patryn who will disrupt this alliance of the lesser races in their struggle to gain control of all four worlds. Only Alfred and Haplo realize that they have a much older -- and more powerful -- enemy than each other...
This entire series was very good. Definitely recommended.