As a drama, “The Americans” struggles to crack a certain code; the concept is tantalizing, but the follow-through lacks the momentum that gets viewers to commit. Russell initially brings a steely-eyed edge to her role, but after a couple of episodes, it’s almost too cold, too blank. Rhys, on the other hand, runs away with the show as Philip, forging a character who is brutally efficient, hotheaded and yet sympathetically vulnerable. Right away you want to know a whole lot more about him than you want to know about her, which gives the series a slight imbalance even as the two actors complement each other.

And as an exercise in nostalgia, “The Americans” succeeds only partly. Washingtonians hoping to retrieve the drab grit and utter Hinckleyness of the city in 1981 will probably be let down, even though the show seems to take its wide-frame glasses and three-piece suits seriously. The espionage is so yesteryear that it verges on comical (which it often did in reality, too); in the second episode, for example, Elizabeth and Philip launch a convoluted scheme to wiretap Defense Secretary Caspar Weinberger’s home office. This requires, in no particular order, a false mustache, a stolen clock, the administering of a poison to which only one antidote exists and the act of hooking up a bunch of equipment straight out of the glory days of Radio Shack.