Although Theodosia Browning barely knows a Phalinopsis from a Bog Rose, she still enjoys Charleston's Spring Plantation Ramble, especially since she can promote her Indigo Tea Shop and her latest concoction, Dragonwell Sweet Tea. But the party's over when Mark Congdon wins a bid for a rare orchid-and promptly dies. It looks like a simple heart attack, but Theo suspects that someone purposely turned his green thumb blue