Dangerous Assignment 50/05/17 (ep020) The Lost City

Dangerous Assignment was an NBC radio drama starring Brian Donlevy broadcast in the US 1949–1953, a syndicated television series distributed in the US 1951–52 (also starring Brian Donlevy), and an Australian radio series broadcast in 1954-56 as remakes of the original American radio scripts.

Series premise
"The Commissioner" sent US special agent Steve Mitchell to exotic locales all over the world, where he would encounter adventure and international intrigue in pursuit of some secret. Each show would always open with a brief teaser scene from the episode to follow. After the intro, Steve Mitchell would be summoned to the office of 'The Commissioner', the regional head of an unnamed US State Department agency created to address international unrest as it affected U.S. interests.

"The Commissioner" would give background information, explain the current situation and tell Steve his assignment. Steve's cover identity, in almost all his adventures, was that of a suave debonair foreign correspondent for an unnamed print publication — his assignments invariably involved deceit, trickery, and violence, all tied together into a successful resolution by the end of the episode.
RADIO SERIES
Dangerous Assignment started out as a replacement radio series broadcast in the US on the NBC radio network in the summer of 1949; it became a syndicated series in early 1950. Reportedly, star Brian Donlevy himself was the one who brought the show to NBC.

In the American radio shows, Donlevy was both the protagonist within the action and the narrator, giving the show "a suspenseful immediacy." The only other regular actor on the radio shows was Herb Butterfield, who played "The Commissioner." Many stage and screen actors appeared as guest-stars including, among many others, William Conrad, Raymond Burr, Paul Frees, Jim Davis, Dan O'Herlihy, Richard Boone, and Eddie Cantor.