Between friendship and betrayal.

Lena is having a hard time adjusting to ordinary life. How can she forget Dante, the boy whose eyes are different colours? But she soon has much bigger worries. On a school trip she realises that her pursuers haven't given up after all. At the last minute, Lena manages to pass the chronometer she uses to travel through time to her friend Bobbie. A fateful mistake. Fleeing, Bobbie stumbles into the past and becomes trapped in time.

Lena breaks her promise and returns to the invisible city. She needs Dante's help. But her enemies are a step ahead of her. Lena must save not only Bobbie but the whole invisible world...