Em Hansen works as a mudlogger among a mostly coarse crew of working men. Though she suffers the ill will of the majority, Em is doggedly attached to her work, which involves recording data about mud samples, even as the arrival of a coolly elegant woman geologist increases the sexism quotient. The first death claims Em's mentor Bill, a careful man whose car skids out of control; next to go is young Willie, apparently crushed to death by wild horses. Although remaining an outsider among the crew, Em sets out to investigate the cause of the deaths, which may be linked to the oil field's profitability.