A Touch of Mistletoe by Julia Byrne

It’s Christmas, and Gideon Heywood, Viscount Rotherham has been sent to the country to investigate a murder. When the local magistrate invites Gideon to spend Christmas with his family, Gideon is reluctant—his host has several daughters and Gideon has no desire to spend Christmas fending off marriage-bait—but there’s no polite way to refuse so he resolves to keep his distance from the daughters.
Unfortunately for this plan, not twenty minutes after his arrival, he’s knocked off his feet—literally—by Miss Sophie Warrington, the eldest daughter of the house. She’s chaotic and warm-hearted and impulsive, and nothing like the kind of woman he intends to marry, but somehow Gideon can’t seem to stay away from her.
Sophie doesn’t know quite what to make of her father’s guest. Rotherham is not only dark and dangerous and unlike every man she’s ever met, he’s also downright disapproving. But…there’s something about him that makes her want to get to know him better. Helping him with his murder investigation seems an excellent way of achieving that goal—if only she can get him to discuss the case with her.
But the murderer is closer than they know, and when the truth comes out it will threaten everything Sophie holds dear.