One of Our Spies Is Missing is the 1966 feature-length film version of The Man from U.N.C.L.E.'s second season two-part episode "The Bridge of Lions Affair". The episodes were originally broadcast in the United States on February 4, 1966 and February 11, 1966 on NBC. It, as does the television series, stars Robert Vaughn and David McCallum. It is the fourth such feature film that used as its basis a reedited version of one or more episodes from the series. However, this film, and the episodes it draws from, represents the only instance where a Man from U.N.C.L.E. story is derived from an existing novel: The Bridge of Lions (1963) by Henry Slesar.