The Color of Death — Elizabeth Lowell

The fourth book in the Rarities Unlimited series

Kate Chandler has accepted a commission that will solidify her reputation as a world-class gem cutter. But during what should have been a simple transfer, seven rare, priceless sapphires vanish without a trace, along with their courier, her brother Lee, who now, quite possibly, is dead. And suddenly Kate is on the run, pursued by federal agents who believe she's the criminal mastermind of a cunning bait-and-switch.

Only Kate suspects the terrifying truth: that she's stumbled into a conspiracy of deceit, betrayal, and cold-blooded murder that goes far beyond a simple jewel heist. Getting Sam Groves, the FBI special agent who's her constant shadow, to trust her is a step in the right direction--but it may be too little and too late in a bloody game where terror dictates her every move. Because a ruthless assassin has already received the order that Kate Chandler must die .. .