After a few episodes of giant, undersea monsters, amphibian people, and "Manchurian Candidate" - style brainwashing, this return to a more grounded, "realistic" cloak-and-dagger foreign agent meance type of story seems a little lackluster.
Involves Adm. Nelson being forced to turn over a map of strategically important sites to traitorous military officer; mainly notable for guest stars George Sanders and Susan Flannery (The Bold and the Beautiful), the latter of which plays the Adm.'s "sister". At the beginning she's able to fend off two would-be abductors, and by the end of the story you find out why.