Otello Morsiani, a north-eastern-italian lawyer, takes the job of estimating land holdings on the Po Delta, which are intended to be expropriated to make way for a national park. The lawyer soon discovers that in that area, once target of methane extraction, the soil is now at risk to sink, due to hydrogeological disturbance: in the meanwhile, he also digs out a mystery tied to a death dating back twenty years before.