An Agent for Darcy - Pinkerton Matchmakers, #16

Widow Darcy Spencer abhors the very idea of marriage, but to become a Pinkerton agent, she must marry her trainer. She's assured that it's in name only, so she begrudgingly takes the position. Although her new husband is infuriating, she's determined to prove herself worthy as an agent - and as a person. Agent Porter Shaw can't help but tease his tight-lipped, stubborn bride. She keeps her secrets locked up so dang tight that even his usual charm fails to break through her defenses.
When they are assigned a case at a cattle ranch in the Rocky Mountains, they quickly discover that someone is very serious about keeping their own secrets buried. Can a jaded widow and a cocky agent learn to work together, and maybe even find love?