Definition of "in the dark"
prepositional phrase (idiomatic) Without information . quotations examples
Quotations Until two or three days before Carter 's December 15 announcement , the State Department spokesman was still saying that no decisions had been reached on the timing and the modality for normalization of relations with Peking . Meanwhile , the administration had been keeping Congress , including its leadership , completely in the dark Then , taking advantage of the Christmas holidays , during which no one was watching on Capitol Hill , Carter sprang his surprise .
1983, James C. H. Shen, “Beginnings of Endings”, in Robert Myers, editor, The U.S. & Free China: How the U.S. Sold Out Its Ally, Washington, D.C.: Acropolis Books Ltd., page 18