Take A Highlander by Rebecca Preston

When the ancient stones reveal their hidden secret, Eva finds herself ensnared in a web of time and intrigue with a handsome Laird…

Eva Matheson, a tireless investigator for Child Protective Services in Chicago, is in dire need of a break. But her getaway takes an unexpected turn when she steps through a concealed doorway beneath the ruins of a castle and is thrust back in time. Lost and disoriented, she faces accusations of witchcraft in a land where legends and magic reign.
In a time when belief in the supernatural is rampant, Eva finds an unexpected ally in Finlay, a single father and harpist, who is both captivated by her and the proof of her time-travel. As they navigate the treacherous world of 18th-century Scotland, their growing bond is tested when a rival clan’s heir is found murdered, and all eyes turn to the newcomer who holds Finlay’s heart.