The Shadowy Horses by Susanna Kearsley

Verity Grey arrives in Scotland to join in on an archaeological dig, one that she doesn't know all the details to until she arrives. Her employer, the eccentric old Peter Quinnell believes he has found the sight of the resting place of the Ninth Legion – a Roman legion who mysteriously disappeared around 177 A.D. The thing is, he doesn't have any kind of physical evidence. He's only going by what a local boy – who appears to have 'the sight'- has said. The boy has supposedly seen a Sentinel walking about – a Roman solider.

Verity has her doubts, of course, but finds herself growing more fond of Quinnell and stays on to help. After hearing invisible horses at night, and being followed around by a ghost (the Sentinel) who seems determined to warn her about something, she starts to believe.

I loved the archaeological aspects - going through the dirt bit by bit - with the anticipation of finding something. And the odd cast of characters rounds out another great book by Susanna Kearsley.

The Shadowy Horses had the right balance of suspense, history, the beautiful sights, and a bit of romance.