The Resonance Frequency

She needs a battery. He is the spark.

Dr. Mara Kline is no longer just a physicist lost in 1385; she is the only thing standing between history and total collapse. The ruthless time-traveler Aris has seized the Tower of London, turning the medieval fortress into a high-tech reactor that threatens to enslave the past to save the future.

Mara has a plan to stop her: an EMP blast that will fry Aris's machines and reset the timeline. There is just one problem. Her device is dead.

Elias Rowan has sworn to protect the strange woman who fell from the sky, but the road to London tests him in ways steel and fire never could. He must guide Mara through a war-torn winter, fighting enemies armored in synthetic alloys, all while protecting a secret that could get them killed.

But the solution to their power problem is dangerous. To recharge the Tether, Mara needs a massive surge of bio-feedback energy. Adrenaline. Intense physical connection.

As they race against the clock, the line between tactical necessity and raw desire blurs. To save the world, they have to burn together. But when the smoke clears, Mara will face an impossible choice: return to the safety of the 21st century, or stay in the mud and blood with the man who holds her heart.