The Twilight Prisoner by Katherine Marsh

Jack Perdu once entered the lands of the dead to find the spirit of his mother. To do so, he needed a Golden Bough, an object that permitted him to enter the Underworld. During his time there, he met and befriended a Ghost girl named Euri, and when Jack finally returned to the world of the living, they promised to keep in touch.

Months later, Jack is attending George C. Chapman High School, and is falling in love with a girl named Cora, who is in his classes and in Latin Club. He wants to ask her out, but this is the first girl he's ever really liked, and he's hesitant because he isn't sure if she likes him, too.

But something else is wrong- Jack can still see Ghosts. He had supposed that when he escaped the underworld in the last book, he would have lost that ability. But he hasn't. And now Jack suspects something is wrong- with him. So when he does manage to ask Cora to meet him, he plans on showing her the Cyclotron underneath the college where his Dad teaches. Only fellow schoolmate Austin comes along for the ride, making Jack annoyed. He wanted to be alone with Cora, not Cora and Austin.

But in their travels in the tunnels under the college, Jack realizes he can show Cora something better than an old Cyclotron- he can show her the Underworld! And so the three of them cross into the Underworld. But Cerberus, the guardian, scents them immediately and gives chase. Jack tells Austin to run, and flees with Cora, where they find Euri, who keeps them safe from Cerberus, at least for the moment.

Jack finds Euri... different. Darker than he remembered, and smaller and younger as well. She's not happy to see Jack with Cora, but he asks for her help, and she unbends enough to give it to him. Cora is frantic at being trapped in the Underworld when she realizes what is happening, and insists on being taken to see her mother. But when they travel there, Jack realizes that Cora isn't as rich as some of the kids at the school, and her mother is sick. Cora not only attends the school on a scholarship, but takes care of her mom in the bargain.

Jack and Cora must escape the city. Only, since the last time he wound up in the Underworld, things have changed, and *not* for the better. The Underworld police are being more stringent than ever, and all the exits to the human world are under a strict watch. The place where Jack escaped the last time is now under guard, and Jack, Cora and Euri must find a new place to escape.

To do that, they must find the Ghost of Egbert Viele, the man who laid out the city's water plan and surveyed the city to find the underground waterways. He would know where there are hidden springs or streams that would allow Jack and Cora to escape. But he's much harder to find than Jack and Euri anticipated, and Cora doesn't know that there is a time limit on their ability to escape the Underworld. Worse still, Austin also appears to be in the Underworld, and he didn't escape like Jack told him to. And with the revelation that Euri has become a Poltergeist, everything Jack knows about the Underworld seems to have changed.

Can Jack and Cora find Viele, find a hidden spring, and cross over, escaping the Underworld before their three days are up and they both die? Why does Jack seem to be nothing more than a Ghost, despite being alive? And can Jack confess his love to Cora without being completely shot down? Even if she does love him, will her love survive his lying to her about the Underworld? And can Jack save Euri from becoming something very dark in spirit terms?

This was an interesting follow up to "The Night Tourist". Though the other book seemed like it was complete in itself, this one takes up after the other one leaves off, and the ending of this one just cries out for a sequel, which means it will probably end up being a trilogy.

The big mysteries in this book are: Why does Jack appear to be a ghost in the underworld rather than a living person? We never get an answer for that, exactly, but we are told that Jack can choose what he wants to be. And my feeling is that this is because Jack's mother used to be a Ghost before Jack's father rescued her, so Jack inherited a sort of "half-ghostly" quality from her, but it wasn't activated until he visited the Underworld in the last book. The second mystery is: Does Cora return Jack's affections? And yes, that one is answered, and definitively.

I can almost feel sorry for Jack, but I can tell what sort of book the third volume is going to be, and I hope there is a happy ending for both Jack and Euri at the end of it- it's by no means guaranteed, but the fact that Jack can be either fully human or fully a ghost means twice as many chances for them to be happy. But what will he choose in the end, or will Euri choose to move on? I don't know, but I recommend this book anyway.