This one really keeps you on the edge, because you don't know if Cinnamon has gotten too deep into her role--and neither does Dan!
Fetyukov is a "short-tailed spy": he has no relatives that his superiors can threaten in order to keep him in line. He's also killed at least 30 agents--including women. Nice company for Cinnamon to keep.
Complication piles on complication. Fetyukov knows that Cinnamon is an American agent--and Cinnamon knows that he knows. Older agent Shtemenko knows, too. Cinnamon and Fetyukov carefully dance around the situation, seeming to ignore what is to come. The way that they cut from scene to scene--dancing, playing tennis, picnicking at the beach and in a park--was well done, compressing six days into a short period.
At one point, Dan seems to lose track of just what he is doing. He and Barney set up Shtemenko to attempt an assassination--only to catch and thoroughly photograph him. They then order him to leave the country or be exposed. They want it to seem that Fetyukov was the one to set him up, just to get him out of the way. Shtemenko reacts by confronting Fetyukov at Cinnamon's apartment and nearly killing him. Cinnamon prevents him from doing so, and Fetyukov contemptuously throws Shtemenko out. The next day, Dan comments that the reason Shtemenko did not leave the country was that he had died of a heart attack. Ummm...they never actually meant Shtemenko to leave the country, so why would Dan have been surprised that he didn't do so?
Having Shtemenko kill Fetyukov would have made the mission a sucess...so was Cinnamon supposed to save Fetyukov at that point? Had Dan expected Shtemenko to kill Fetyukov, then flee?
Quite an eye-opener for the mid-Sixties--the scene cuts make it rather clear that Fetyukov spent the night with Cinnamon.
Fetyukov indicates that he wants to defect, and Cinnamon runs off to tell Dan. Fetyukov follows her to the hotel room where Dan, Barney and Professor Napolsky are staying--only to find that Cinnamon has removed the bullets from his gun.
This ending scene is rather ambiguous. Dan wonders why Cinnamon started telling him all that nonsense about Fetyukov wanting to defect. Cinnamon claims that Fetyukov would, of course, need to know just what hotel room to break into--and she did indeed speak rather loudly to Dan. Also, when we see Fetyukov and Cinnamon looking eye-to-eye, Cinnamon's expression looks rather complacent, as though he has reacted just as she planned. However, she then walks up and cracks him across the face. When they set up the photographs of Fetyukov, they include one of Cinnamon slapping him--but why did she slap him the first time? Why did she end up staring out the window with a rather troubled look on her face?