When seventeen-year-old Gracie Hart gets caught stealing a ride on a circus train, she expects to be arrested. Instead, she is offered a job as the assistant to the circus magician and knife-thrower, Jack. He's charismatic and genteel but his aim isn't perfect--hence the position opening.
Once Gracie starts performing with Jack, she begins finding threatening notes hidden in her costume. At first she thinks she's being haunted by the ghost of the last assistant, but Gracie soon realizes she's the one trying to warn herself: she's next.
Every time Gracie steps inside the magician's vanishing closet, she is transported from the late nineteenth century to Knossos, a flying fortress with the technology to turn people into gemstones. While there, she discovers the last assistant's death wasn't an accident, and that Knossos's dubious ruler may have a hidden agenda of her own.
Unfortunately, Gracie forgets everything whenever she steps back through the closet. Gracie suspects Jack and his identical twin know something about her reoccurring déjà vu and the cryptic notes, but she's not sure which brother she can confide in.
She has several reasons not to trust either, and even more cause to believe one of them holds the answer she needs to save herself from insanity. Too bad for Gracie, there seems no definite way to tell them apart. A second death on the circus lot makes one thing clear: if Gracie can't figure out the mysteries under the big top, her next venue might be the afterlife.