Here's the blurb:
Simon's sister and Flora's brother are prisoners of the Broken King, and they have entered his land determined to rescue them. But here, nothing is quite what it seems. Who can Simon and Flora trust? What does Pike, their mysterious companion, stand to gain? As rumours of war and revolution swirl around them, and as the sinister Knight of the Swan dogs their every move, the pair must confront their terrifying final task. And if they can free their siblings, will they then be able to open the way between the worlds, and return home?"