This is book 6 in a series. It's therefore not the best place to start reading, and I can guarantee that the review will contain spoilers for at least some of the other books that have come before. If you haven't read these books, run, don't walk to a bookstore or a library, and get started.
When several of the Pack's children threaten to turn Loup, and may have to be killed, mercenary bad-ass Kate Daniels and her mate Curran, the Beast Lord of the Pack realize that they need to get their hands on more panacea, a herbal concoction that ensures the survival of most of the young shapeshifters. It's obvious to both of them that the invitation they have received from a couple of European packs is a big ol' trap, but they're offered so much of the precious panacea (which they have absolutely no way of making themselves), that they simply cannot afford to refuse. So Kate and Curran ally with someone they normally wouldn't trust, gather up a band of their best fighters, and set off to Eastern Europe on an adventure.
Once they get there, they quickly discover that it was indeed a trap, but one of a completely different nature than expected (I may have cheered at this revelation). The Pack are far away from home, and the task they've been set, to guard a pregnant shapeshifter princess until she gives birth, is not an easy one. The biggest danger may be to Kate and Curran's relationship, however.
This is the road trip book, the one where the authors take the characters out of their established comfort zone (even if that is a zone frequently fraught with incredible danger, and near death experiences) and move them somewhere, with new and exciting challenges and threats to their lives and safety. During the journey, the Pack encounter pirates, and I may have been rather vocal in my appreciation of the type of shapeshifter they turn out to be. I love how creative this author team is with their world building.
Then they arrive in Eastern Europe, with rivalling shapeshifter clans, to do a job that seems nearly impossible to complete without sparking some sort of turf war. Kate, who's still getting used to not isolating herself and trusting no one, experiences jealousy for the first time, and starts questioning Curran's devotion to her, especially as she's dismissed by all the European shifters as the Beast Lord's human plaything. Why wouldn't he want a powerful shifter girl instead? I must admit, invested as I was in Kate and Curran's relationship and happiness, I was extremely unhappy with this part of the book, and I wanted to punch Curran in his pretty face for what he was doing to Kate. Of course it turns out to be a lot more complex than Kate knows, and Curran has very good reasons for what he's doing, but even after I found out what was going on, I was not happy with him. There is a great explanation for why both Kate and Curran acted the way they do on Ilona Andrews' blog, where the authors answer FAQ about the recent book - don't read it until AFTER you've finished the book, there are spoilers!
Because of the jealousy drama, this doesn't quite get included among my favourite Kate Daniels books, but it's a wonderful read. I laughed, I cheered, I cursed and bit my knuckles in suspenseful scenes. Reading an Ilona Andrews book tends to be quite an emotional rollercoaster, and while they always end on a happy note, there are very real dangers in each book, and casualties along the way. Don't be sure everyone's going to make it out unscarred, or even alive. I'm so glad this book got Ilona and Gordon to the top of the NYT Bestseller list, they deserve it.