Fastest Kill by Alessa Thorn

A charmer with a secret. An assassin with zero tolerance. A rivalry that’s about to burn them both alive…

Dario Colleoni has spent his life being the one everyone underestimates, the charming one with a drink in his hand and a secret he’s kept since the night his father died. With Rodrigo finally happy and Leo settled in love, Dario should be celebrating. Instead, he’s drinking his way across Istanbul, haunted by the woman who shot his client two years ago and left him a bullet casing with a heart carved into it.
Frederica Alesci doesn’t do soft. She doesn’t miss, doesn’t fail, and certainly doesn’t tolerate love. So when she ends up drunk in a Cretan holding cell at three in the morning, she resents that the one person she can call for help is the infuriating Italian she’s spent two years pretending to hate.
A trip to Rhodes to dig through her father’s records was supposed to be a quick detour on their hunt for Serapis. What Dario and Frederica uncover instead is a trail of stolen artifacts, a five-hundred-year-old enemy the Colleoni’s and Edgeworth’s never knew existed, and the kind of partnership that turns professional rivalry into something neither of them is ready for.

Please note this is the final book of ‘Mercenaries and Magic,’ so go and start at Book 1, ‘Darkest Night,‘ if you haven’t dived into this world yet. It is an adult dark romance with a splash of magic. It contains graphic action scenes and spice.