All I Want for Christmas Is Her by Harper Cross

Deck the halls with spies and groomsmen…

As an agent for a spy organization known as HEAT, my idea of a thrilling vacation is quiet downtime, settling into my new apartment, and domesticating my skittish foster cat. When my fuzzy roommate tries to scream down the building, I attract unwanted attention, including from Gage Halifax, the sexy do-gooder next door.
Gage loves animals. And kids and the environment. I hate white knights. And nosy neighbors and romantic liaisons. Which is why, despite my steamy fantasies about my hot neighbor, I intend to keep my distance from him.
Until I learn Gage’s company is being courted by a corrupt international organization and he might be in their crosshairs.
When I find out he’s a groomsman in need of a wedding date, I offer to be his plus one in exchange for him helping me plan my first Christmas in the city. It’s the perfect pretext for sticking close to him to protect him. I don’t anticipate how hard it will be to resist my forbidden fantasies. And I can’t guard against his heart of gold melting my heart of ice.

We’ll attend the wedding of the season if enemy agents don’t kill us first. And I’ll blow my cover if I can’t help falling for the guy next door.