Finding an unforgettable (and hopefully unused) title...

[Crystal]

I think I finally have it!!

A Key in the Shadows

Just trying it on for size but I think I like it. :)

[DSL]

I like it too; a big improvement over using your character's name, and it just might work. Though it's hard to say without knowing more about your book and the mood you want to create with your title. A KEY IN THE SHADOWS feels eerie yet optimistic. It tells the reader there will be a happy ending after some fumbling around in dark places. For a younger audience, that could be a good thing. LOCKED IN DARKNESS, on the other hand, is more foreboding. THE LOST KEY, more uncertain. Play with the words when you have bits of extra time. Let them cook and simmer awhile. And in the end, don't stress it too much (or become too attached), because what really impresses publishers/agents is the writing. An editor I admire once told me that most writers struggle with titles, and they're frequently changed anyway.