The Viognier Vendetta by Ellen Crosby

 Though this is part of the Wine Country series, most of the action takes place in Washington DC.

Vineyard owner Lucie gets a call from her long-lost college roommate, Rebecca, inviting to a ceremony because her rich financier boss, Thomas, is donating his collection of papers to the Library of Congress. Because their friendship had ended abruptly, Lucie doesn't really want to go but she does--and gets swept into a mystery when Rebecca disappears before the event. Then Lucie finds out Rebecca may have been involved in uncovering a financial scandal at her firm. And things keep getting murkier and more dangerous.

At the same time, back at the vineyard, Quinn, Lucie's head winemaker and sometime boyfriend is talking about buying his own vineyard. She justifiably wants to know if he's planning on leaving and he's very vague, which is not helping their relationship. So there's a lot of stress for poor Lucie.

Vendetta is another charming tale from this series. And I learned a lot about Washington DC that I never knew before.