Em Hansen, unemployed professional geologist, sometime FBI consultant, and part-time master's student, has fallen into a rut. Sure, she's helping her best friend, Faye Carter, cope with a new baby and the death of her FBI agent husband - something Em feels partially responsible for, as Tom was her mentor at the Bureau. However, deep down Em knows she's really just marking time until she gets motivated to do what she needs to - finish her master's, look for a job, put Tom's death behind her, and get on with her life.

Em is finally forced out of her lethargy by an unusual case: A friend of Faye's is looking for someone to authenticate a painting, a nocturne by the famous painter of the American West, Frederic Remington, that has been in his family for years. He believes it is a fake, and wants her to use her forensic expertise to analyze the pigments to prove it. What are pigments, in fact, but ground-up minerals, and so it's a perfect task for a geologist. Although Em doesn't quite trust Faye's friend, she sets aside her reluctance and takes the case.

The project takes her from Wyoming and Utah to Washington, D.C., and Pennsylvania. Before long, her innocent research project has taken a sinister twist, and Em finds she's also chasing a murderer. Suddenly it's up to Em to find out what's going on in time to save her own skin.