With their very exciting spy technology and their tried-and-true, toilet-based travel techniques, the InvestiGators are undercover and on the case! And on their first mission together, they have not one but two mysteries to solve! Can Mango and Brash uncover the clues, crack their cases, and corral the crooks--or will the criminals wriggle out of their grasp?

"Hava sails across the sea toward Monsea with her sister, the royal entourage, and the world's only copies of the formulas for the zilfium weapon she saved at the end of 'Winterkeep.' During the crossing, Hava makes an unexpected discovery about one of the ship's crew, but before she can unravel the mystery, storms drive their ship off course, wrecking them in the ice far north of the Royal Continent. The survivors must endure a harrowing trek across...

With her friends divided and scattered, and the Black Swan wanting her to focus on their projects, Sophie is led in a different direction to Stellarlune, which might be their salvation or destruction, and learns the true meaning of power--and evil.