A YOUNG MAN DISAPPEARS in the California wilderness. He leaves behind a gold-flecked rock and a vial of toxic mercury. He is a misfit in the modern world, a throwback to Gold Rush days. A venture capitalist--whose gold country is Silicon Valley--hires forensic geologists Cassie Oldfield and Walter Shaws to track his missing brother. Following one of the 'lost rivers' of the Mother Lode, the geologists plunge into the dark history...