Indiana Jones meets The Mummy only it's medieval and the protagonists are dragons.
If I had quibbles with this one, it's that the h seems to have a chip on her shoulder due to her not being One of Them so to speak - while it is never addressed, it seems certain her father was the ancient and far less human (and thus less empathetic) dragon who was killed in the previous book. I wouldn't find it as vaguely annoying if she wasn't 200 years old or so. That's a long time to not get over it. I also wonder where she's been over the years before she married a ship's captain. She didn't say... She obviously wasn't around the clan.
Anyway... our H is sent on a Quest to find a mighty power source that might ensure that England leave Scotland alone. He finds his way to a ship...somewhere...in France I think. Why France is never explained...or it's explained only in the sense that he feels it less likely that someone in England will hear of it. And they set sail - to some mythical island west of England. Some mythical island that has... what is identified as an elk but sounds more like a moose. Must have been further west than Greenland or Iceland then. In any case, they do find the island, or rather, they get close enough to the island for said power source to find them. Much adventure and errr...interesting times...later, they hunt down said power source and deal with it.
And as with the previous book, it ends with the H/h riding off into the sunset, in this case, sailing.