Stubborn hearts might be the last to fall, but when the hard tumble comes, it’ll last forever. Jonathan Banshire, Viscount Trewellain, has become a bitter, sarcastic lord and against anything remotely smacking of romance. Though engaged to a woman whose hand he’d won in a game of cards years ago, he hasn’t thought of her in years. But he’s also a king’s agent, and as his duty to the Crown, he’s being sent to Spain to track down a missing peer. He goes to escape his personal life. Miss Sophia Wickham is tired of men deciding her future. She’s on a mission to live her life on her terms, but can’t due to an ambiguous engagement to the Viscount Trewellain. Determined to gain her freedom, she sneaks onboard the ship intent to have Jonathan release her from that old promise. When he refuses in a fit of pique, she’s stuck as a stowaway, bound to the one man she can’t stand. In Madrid, they search for not only the missing lord, but also stolen Spanish crown jewels and an ancient relic. Through crashing a glittering ball to hunting down clues to exploring the hidden catacombs and caves beneath Barcelona, the unlikely pair comes to an understanding. Vulnerable and trapped, truths are revealed as well as the fragile state of their hearts. But machinations of a madman bent on revenge could destroy a budding romance, and when the specter of death makes an appearance, Jonathan must finally decide what it is he desires the most.

Even if the world is falling to pieces, when the treasure of the heart is discovered, a fight is needed to keep it. King’s agent, Bentley Courtenay—Lord Castlereagh—has been sent on his first solo mission to rescue a widow, who’s been abandoned in the dense jungles of Venezuela. He intends to bring her back to England to answer questions regarding the poisoning death of a peer. Yet what awaits him in the on the Orinoco River has him wondering why the devil he ever signed up to work for the Crown. Widowed Cora, Lady Trammel, is on a quest to locate a deadly orchid and destroy every last bloom before the toxin she accidentally created can fall into the wrong hands. When she encounters a king’s agent who fires her imagination, she declines his demand to return to London. The fate of the world is at stake, and she has to fix her mistake, for her discovery has the capacity to kill every human on Earth. In the course of the journey, desire flares between Bentley and the older, more experienced Cora, but she’s not looking for love. While he loses his heart, evidence of the fabled city of El Dorado comes to light, and their mission takes a critical turn into dangerous adventure, so matters of love are shelved. Pursued by threats, time is running out to destroy the deadly toxin and protect the world’s greatest treasure from men who mean both to use both for their own insidious gain.

Nothing found in the sands of Egypt is as valuable as the treasure of the heart. Crispin Herrick, the newly minted Duke of Litton is anxiously awaiting his first mission as a King’s agent. Until then, a dig in the King’s Valley he’s sponsoring occupies his time… until he chases down a criminal at the Antiquities Museum. Once he catches her, he’s shocked and delighted to discover she’s the same woman he flirted with in London a year ago, but now she’s as skilled in lying as she is in keeping secrets. Miss Juliana Barrington lives under an assumed identity in Cairo, exiled there when her last mission for the Crown went catastrophically awry. All she wants is to redeem herself by finding a powerful relic before her enemies can, but when her path crosses that of the handsome ex-pawn broker, she can’t help but panic. No matter how her heart twinges, mixing desire with duty is a horrible idea. Crispin and Juliana join forces to find the pieces of the Staff of the Gods, allegedly belonging to Moses himself. Danger dogs their footsteps while romance flickers to life as the days go by, and when the trail leads to a mysterious tomb in the Valley of the Kings, treasure hunting evolves into running for their lives. Staying ahead of disaster is critical; evildoers and death are powerful foes, but hard-fought victory might bring happy endings… if they can survive long enough.