The Girl from U.N.C.L.E.

The High and the Deadly Affair (1x28)

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April poses as an airline stewardess; Mark is disguised as a big game hunter. Both are on board a plane carrying a number of scientists to a Council of World Scientists meeting. One doctor aboard has developed a substance that, carried by harmless birds, can cause slow death to humans. Also on the same flight is the doctor who has developed the antidote. Waverly fears a confrontation between the two hence April and Mark on the scene.