By 1872, the wars across Europe have been brought to a standstill, the tentative peace held in place through the work of secret agents and a collection of inventors and scientists. But tensions are mounting again, and agent Robert "Hart" Hartley-Battridge has uncovered plans that indicate someone is planning to kidnap one of their most brilliant minds—the tempestuous Karol Zieliński

Hart is only too familiar with the hotheaded, beautiful scientist. He spent years working alongside Karol, concealing his love for him, convinced he would have been just one in a string of conquests lured into Karol's bed. Then a mission gone wrong left Hart scarred and near death, and Karol abruptly quit the Service and never approached Hart again. But the new threat is about to close the distance between them. For one day and one night, Karol will have only a single guard to watch over him, and Hart doesn't trust anyone but himself to keep Karol safe.

Twenty-four hours in the presence of the man he loves, a man he hasn't seen in three years. Hart expects Karol to have forgotten him. But Karol remembers their every mission—especially the last. And he has a surprise for Hart so daring and unprecedented it brought danger—and Hart—back to his door. With peace and Karol's life on the line, Hart needs to accept that he was never a conquest. That for him, Karol would change the world.