Inter-monarchial relationships can be tricky things. There are all sorts of things to consider concerning alliances, succession, trade, and so on. Not to mention security — with all the travelling between two countries that will be going on, it makes it easier for someone to, for example, kidnap someone.
When Queen Elspeth is abducted on a state visit to Galorndan, Cullan and his companions are ordered to once again travel several hundred miles to find someone — this time to rescue, not to kill. Although, someone probably will need killing while they're in the area.
