Alone [Book 3 of the Life Hearts Trilogy, previously called Lost Hearts]

Blue is in the clutches of the Watchers. And one of her friends *is* a Watcher, and Martyn betrayed everything he knew, and it's tight and claustrophobic and annoyingly shimmery and...

Basically, she has a lot on her mind.

Gem, meanwhile, is dealing with a bunch of rowdy Last Lifers getting into her world, her twin brother getting "inspired" by an untrustworthy source, and of course, three missing people: Blue, Grian, and some guy who everyone seemed to hate named Martyn.

But there are a lot more problems to solve than those. People and things that are supposed to be gone return, secrets that everyone would rather keep hidden are uncovered, worlds full of citizens are destroyed, and friends who have so much to live for die.

Most of the problems can be traced back to the Watchers, which is why Blue and the rest of the Listener's Chosen are determined to defeat them. But things aren't always what they seem, and it's easy to get sidetracked when there's more than one villain.

If you haven't read Life Hearts (book 1) or Evolved (book 2) go check them out. This will make a lot more sense once you've read those.