Hostage, a person held in captivity to assure that an agreement is observed or to coerce another party into taking (or not taking) some action. Countries in ancient and medieval times sometimes exchanged hostages, often persons of high rank, who could be put to death if certain agreements were broken. Invading armies often take hostages of local citizens to discourage resistance to their occupation. Terrorists sometimes seize hostages both to force concessions from governments and to gain publicity for their cause.
It could happen: As you're rushing to get to the airport, you absentmindedly throw a gassed-up chain saw into your suitcase. Or a bag of live eels. Yes, TSA officials really spotted these items at U.S. airports. And stranger things, too.
Few incidents shaped the U.S. civil rights movement more than the brutal death of Emmett Till. What other murders have sent shock waves through the public psyche?