The Wardens of the Realm are a group with extraordinary abilities, dedicated to protecting England from any threat. But in this steam–powered world, there's a fine line between enemy and ally...

Reeling from her brother's death, beautiful American spy Claire Brooks has vowed revenge on the member of The Company who she believes to be responsible: Stanton Howard. But when she chases the man to London, Claire is captured by the Wardens of the Realm and placed in the custody of the Earl of Wolfred, the dashing Alistair Payne.

Seeing the prospect of retribution slipping away, Claire convinces Alistair that she has defected and will help him take down The Company. As they travel via steam liner, Claire and Alistair must pretend to be engaged. Claire can't deny the growing attraction she feels for her pretend husband, but when Howard is finally within her reach, she will have to decide whether her true loyalties lie with The Company or with her heart...