Loyalty’s Betrayal by Mari Carr

Head of security for the world’s most powerful secret society isn’t an easy job. Mateo failed in his duties, and people died. When he’s offered a chance to prove himself and unmask a traitor, he accepts without hesitation. His chance for redemption comes with a condition, a deadline…and an ultimatum. The condition? Mateo won’t be working alone. He’s partnered with Cecilia–a brilliant woman who knows more about the Masters’ Admiralty than anyone, and Dimitri, an arrogant man with a dangerous skill set.

The deadline? He has one week to find the traitor or lose his position as captain of the Spartan Guard. The ultimatum? Cecilia and Dimitri think Mateo is going to be their third in an arranged menage marriage. They can’t know there’s a chance the union will be dissolved if Mateo finds the traitor in time.