Adapted from Baroness Orczy's novel, a Polish agent and a Russian spy hide letters in candlesticks and then seek to recover them.
At a masque ball in Vienna Grand Duke Peter (Robert Young) meets Maria Orlich (Maureen O'Sullivan) and kisses her. She brings him to a group of Polish nationalists, who demand he write to his father, the Czar, to save Maria's father. Korum (Douglass Dumbrille) gives Baron Stephan Wolensky (William Powell) the letter to take to the Czar. Countess Olga Mironova (Luise Rainer) is told that Wolensky is a Polish agent, and she must cross the Polish border. Wolensky calls on Prince Johann (Henry Stephenson), who asks him to take candlesticks to Princess Tanya. Wolensky hides the letter in one. Olga comes in as he leaves and tells Johann she is going to Petersburg. Korum warns Wolensky that Olga is a Russian spy. Olga persuades Johann to let her take the candlesticks. She is told to get there before Wolensky so that he can be arrested as a Polish agent. She puts the papers in the other candlestick.
At the station Wolensky learns that Olga took the candlesticks on an earlier train. Her maid Mitzi Reisenbach (Bernadene Hayes) helps Anton (Donald Kirke) steal the candlesticks. Peter and Colonel Baron Suroff (Frank Morgan) are held captive. Wolensky sees a notice of jewelry theft from Olga. Anton is arrested, but Mitzi takes the candlesticks. Wolensky offers to help Olga find the candlesticks, and they learn that Anton gave them to a lady. Wolensky and Olga dine and talk of loneliness. Wolensky sneaks out and goes to Budapest to find Mitzi, who says she sold them. Olga follows Wolensky, and they go to Paris looking for them and then to London, where they each buy one. Wolensky finds the order for his arrest, and Olga comes to trade them. He shows her both letters and promises to return her papers later to save her.
Maria protects Peter, and he thanks her. Wolensky gets the letter to the Czar, who pardons Orlich. Suroff and Peter are also released blindfolded, but Peter senses Maria. Col. Radoff (Frank Conroy) orders a search for Wolensky and calls on Olga to arrest her. Wolensky comes in as Radoff hides. Wolensky returns the candlestick with the papers, which Olga throws in the fire. Radoff arrests both; but the Czar pardons them for their love and bravery. In the final scene Wolensky and Olga ride in a sleigh and plan to marry.
This romantic drama of international intrigue is rather improbable but dramatic nonetheless. For the sake of love even the Czar pardons a wanted spy. Oh, that powerful men might often be so kind!