These are the stories that defy conventional logic. The proverbial vanished without a trace incidences, which happen a lot more (and a lot closer to your backyard) than almost anyone thinks. These are the missing whose situations are the hardest on loved ones left behind. The cases that are an embarrassment for park superintendents, rangers, and law enforcement charged with Search & Rescue.

Americans have long been taught that events such as the notorious My Lai massacre were "isolated incidents" in the Vietnam War, carried out by a few "bad apples." However, as award-winning journalist and historian Nick Turse demonstrates in this pioneering investigation, violence against Vietnamese civilians was not at all exceptional. Rather, it was pervasive and systematic, the predictable consequence of official orders to "kill anything that moves."

In April of 1846, 21-year-old Sarah Graves, intent on a better future, set out west from Illinois with her new husband, her parents, and eight siblings. Seven months later, after joining a party of pioneers led by George Donner, they reached the Sierra Nevada Mountains as the first heavy snows of the season closed the pass ahead of them. In early December, starving and desperate, Sarah and 14 others set out for California on snowshoes and over the next 32 days endured almost unfathomable hardships and horrors.

April 25, 1986 in Chernobyl was a turning point in world history. The disaster not only changed the world’s perception of nuclear power and the science that spawned it, but also our understanding of the planet’s delicate ecology. With the images of the abandoned homes and playgrounds beyond the barbed wire of the 30-kilometer Exclusion Zone, the rusting graveyards of contaminated trucks and helicopters, the farmland lashed with black rain, the event fixed for all time the notion of radiation as an invisible killer.

In February 1959, a group of nine experienced hikers in the Russian Ural Mountains died mysteriously on an elevation known as Dead Mountain. Eerie aspects of the incident—unexplained violent injuries, signs that they cut open and fled the tent without proper clothing or shoes, a strange final photograph taken by one of the hikers, and elevated levels of radiation found on some of their clothes—have led to decades of speculation over what really happened.