Sentence:  The French missionaries aided the mothers of Argentina's <WSD>desaparecidos</WSD> by accompanying them to police stations and military barracks looking for news of their children, before being kidnapped themselves by Astiz. 
Meaning of the word marked with <WSD> tags:  One of the people who disappeared during the 1976-1983 military rule in Argentina, presumed to have been killed by members of the regime.