Lissa Yellowbird-Chase shook a shovel-full of damp clay onto the banks of the Little Missouri River, all the while watching for signs: metal pins and plates, cigarette butts, jewelry, fabric, or bone.

“You just kind of shake it out, you don’t just pile it,” she said as the soil slipped off her shovel. “You end up with a finger or something in there then you’re destroying evidence.”

Somewhere underneath the mud and dirt, Lissa Yellowbird-Chase suspected that the final remains of Kristopher “KC” Clarke would be found. Killed in 2012 in the Bakken oil fields on the Fort Berthold Reservation in a murder-for-hire scheme, Clarke’s accused assassins await trial for the crime, but his body has never been found. Yellowbird-Chase and a handful of other volunteers, known as the Sahnish Scouts, have been searching for him ever since.

They’ve also been searching for others that have disappeared from the area: Joseph Lee, whose empty car, boots and socks were found in 2013; 74-year-old Ron Johnson, who vanished with his gold Cadillac Fleetwood after leaving the Four Bears Casino and Lodge in 2011; and Reachelle Smith, Yellowbird-Chase’s four-year-old neighbor that disappeared in 2006 from the town of Minot, North Dakota.