In the fifth-season finale of “The Americans,” Elizabeth Jennings (Keri Russell), a covert Soviet agent in the United States, offered some advice to a young Vietnamese counterpart: Get a partner. “You’re not going to make it,” she warned him. “It’s too hard, the work we do, to do it alone.”

Now, Elizabeth is doing it alone.

At the outset of the sixth and final season, which begins Wednesday on FX, three years have passed since Elizabeth’s husband and collaborator, Philip (Matthew Rhys), burned out and left the spy game.

Their cover — suburban Virginia parents running a travel agency — has become his real life. While he books international tours, she’s fomenting the international revolution, alone and wearily, and the strain is showing.