A society woman volunteers to root out enemy agents in Albania.

Montclair, New Jersey widow Mrs. Emily Pollifax, who has decided that she wants to do more with her life than garden and volunteer, enters CIA headquarters and tells Mason, a mid-level administrator, that she wants to be a spy. Although she has been given an introduction by a senator, Mason presses a silent alarm to have their conversation secretly observed via closed-circuit television. Mason dismisses Mrs. Pollifax, but his superior, Carstairs, who is impressed by her intelligence and grit, decides that she would be perfect for a small assignment. After the CIA conducts a background check on Mrs. Pollifax, Carstairs gives her an assignment in Mexico City where, using her own name, she will behave as any American tourist would. Then, on a predetermined date and time, she will go to a particular bookshop, where a copy of Charles Dickens' A Tale of Two Cities will be in the window. Using a coded script, she will then buy the book from the proprietor, DeGamez. Although Mason worries that the assignment, to pick up sensitive microfilm that will be delivered to the bookstore by field agent Tupok, is dangerous, Carstairs assures Mrs. Pollifax that no danger will be involved, much to her disappointment. As Mrs. Pollifax arrives in Mexico City and begins her sightseeing, Tupok is killed. When he does not arrive at the bookshop, DeGamez realizes that the operation has been compromised and does not put the book in the window. The next day, though, another American agent brings the microfilm to DeGamez and tells him that it would be safer to place the microfilm inside a deck of cards. Later, when Mrs. Pollifax, frustrated after several days of passing the shop and not seeing the book, hesitates at the entrance, she is invited inside by DeGamez, who recognizes her from her CIA photograph but pretends not to know who she is. DeGamez charms her into buying a book on solitaire, then nonchalantly tosses her a free pack of cards to go with it. The next day, just before she is supposed to leave Mexico City, Mrs. Pollifax makes one last trip to the shop and sees a copy of A Tale of Two Cities in the window. She enters the shop and speaks the code words but is surprised that the proprietor, who says that he is DeGamez, is not the man she met before. Claiming that the other DeGamez is his cousin, the man offers Mrs. Pollifax coffee, which is drugged, putting her into a deep sleep. When she awakens, she is inside a plane, handcuffed to American agent Johnny Farrell. Through the course of a long plane ride, they banter about which one of them can be trusted, but soon develop a mutual respect and affection for each other. When the plane lands, they discover that they are in Communist Albania. After being escorted to a prison in the hills, Farrell and Mrs. Pollifax are thrown into a cell. Farrell is questioned first, and badly beaten, but Red Chinese Gen. Perdido, the man who posed as DeGamez in the bookshop, does not beat Mrs. Pollifax, even though he is convinced that her proclamations of being an ordinary American tourist are lies. When Farrell is next questioned, he tries to escape but is shot in the leg and returned to their cell delirious with fever and pain. With little more than a knife from Col. Nexdhet, an Albanian patriot who dislikes the Chinese influence in his country, Mrs. Pollifax removes the bullet, after which an angry Perdido relates that he is going to leave the prison and not return until Farrell is able to talk again. During Perdido's absence, Farrell slowly recuperates, while Mrs. Pollifax becomes friendly with her jailers, especially Nexdhet and kind young Sgt. Lulash. Nexdhet allows Mrs. Pollifax to walk outside the prison with him, not realizing that her questions about the surrounding countryside are more than passing interest. Because of her enthusiasm, Nexdhet gives her an old book about Albania that contains topographical maps, which Mrs. Pollifax is certain are still reasonably accurate. One afternoon, learning that prison commander Gen. Berisha has a bad back, Mrs. Pollifax gives him a massage and soon earns his admiration and friendship. Her forays through the prison and its environs enable Mrs. Pollifax secretly to collect rocks and other items that could be used in an escape she is planning, as well as information on where small weapons and keys are kept. Each night she returns to her cell and tries to interest Farrell in her escape idea, but he does not return her enthusiasm, instead pointing out all the pitfalls of her plans. The day before Perdido is to return to the prison, Mrs. Pollifax convinces Nexdhet and Berisha that a party they want to hold in her honor should celebrate Christmas because she will not be alive in December. Although saddened by this, Berisha knows that she is right and agrees. Using an evergreen she picks out in the hills, the men hold the Christmas party, with local food, musicians and even brandy from the general's secret supply. As they start to use her solitaire cards for tree decorations, Mrs. Pollifax notices that the eight of hearts has microfilm jutting out from between the paste boards. When the party ends, she is barely able to take the card before anyone else notices, as well as steal a gun from the general's drawer. Late that night, Farrell surprises her by revealing that he has turned the tree, which is now in their cell, into a crutch so that he can make the escape attempt with her. Using a large rock that she has hidden, they knock a guard unconscious, then escape on the prison donkeys. Although they have a good head start, when Perdido returns, he demands that a full-scale search be conducted. Mrs. Pollifax and Farrell manage to elude their pursuers by bribing a local farm couple, who dress them in peasant clothes and allow them to sneak away with their small flock of sheep. Later, Perdido's men catch up to them again but they hide in a corn field until Farrell incapacitates one of the soldiers sent to find them. Meanwhile, Nexdhet looks down the mountain and smiles as he sees Farrell and Mrs. Pollifax escape. When Mrs. Pollifax and Farrell arrive at the river, they take a small boat and row toward the Adriatic Sea. Just before they arrive at the mouth of the Adriatic, though, Perdido and his men race toward them in a speedboat. Because Perdido wants to question them, he orders his men not to kill them but plans to ram their boat. Mrs. Pollifax and Farrell jump into the water, but, unknown to them, Lulash, who is helming Perdido's boat, deliberately causes it to crash into the rocks. As Perdido screams for Lulash, Lulash swims toward Mrs. Pollifax and Farrell, letting them know that he is their friend. Some time later, at CIA headquarters, Mrs. Pollifax and Farrell listen to taped recollections of their experiences and confirm that everything is true. Carstairs thanks them for their help and, in appreciation, gives them trench coats. Mrs. Pollifax asks that Lulash, who has defected, be processed quickly, then happily walks out with Farrell, as they help each other on with their trench coats.