Early in the Civil War, the Second Battle of Bull Run is a disaster for the North.  At a camp show for Union soldiers, performer Gail Loveless is recruited to become a spy by her friend, Pauline Cushman, who is herself a spy known as "Operator 27."  Working for agent Major Allen Pinkerton, Gail agrees to become a spy known by the code name "Operator 13."  She then goes South with Pauline to the headquarters of Confederate General "Jeb" Stuart.

Posing as Pauline's black maid, Gail encounters Captain Jack Gailliard, a Confederate officer, when he rides by her washing and ruins it.  Jack is a spy for the South, and when Pauline asks too many questions about him at a ball that evening, he and Captain Cornelius Channing become suspicious and have her room searched.

Meanwhile, a traveling medicine show run by Doctor Hitchcock, who is secretly a captain in the Northern army, arrives looking for Operators 27 and 13.  Gail is able to transfer information about Confederate troop movements to Hitchcock just as Pauline is being arrested.  Gail is also suspected of being a spy, but when she is brought to testify at Pauline's trial, she divulges Pauline's real identity and says that her mistress "turned Yankee."  Pauline is then sentenced to death, but Gail and Hitchcock help her to escape.

Back in Washington, Pinkerton knows that Pauline can no longer operate across enemy lines, so he entrusts Gail with the mission to learn more about the activities of Jack, whom Pinkerton suspects is working with "Copperheads," Southern sympathizers, who live in the North.  To make herself believable, Gail, using the name "Anne Claybourne," openly jeers at marching Union soldiers.  She and a man posing as her father are then "arrested."  When the incident is reported in Southern newspapers, "Anne" becomes a heroine and is deported to Richmond, where she becomes the guest of Mrs. Shackleford and her daughter Eleanor.

Gail also re-encounters Jack, who is attracted to her, but suspects that he has seen her before.  While at the Shackleford's, Gail is able to pass on information to the North that results in an important victory, but which causes the death of Eleanor's fiancée, John Pelham, just a few hours before their wedding.  Feeling guilty over her part in John's death, Gail goes into the garden to cry and is met by Jack, who tells her that he loves her.  Because she has also fallen in love with him, she moves him out of the aim of one of her operatives who is spying on them from the bushes.

Soon, however, she gets away from Jack and, dressed in a Confederate soldier's uniform, heads North after the operative tells her that the Confederates now know she is a spy.  As Jack and Channing chase her into the woods, they split up and Jack finds Gail asleep in a spring house.  He then angrily calls her a a traitor and vows to take her back for a court-martial.  He handcuffs Gail, but as they leave the house, they see Union soldiers execute Channing.  Gail's operative then rushes toward the soldiers, but because of his rebel uniform, he is shot.  The Union soldiers then engage the Confederate troops right outside where Gail and Jack are hiding, and Jack leaves Gail by blending in with the retreating Confederate soldiers.

Although they part, a few years later, the war is finally over and Gail and Jack reunite and pledge their love to each other.

Notes
Robert W. Chambers' novel was serialized in Hearst's International-Cosmopolitan, and the film credits the source as "The Stories of Robert W. Chambers," rather than the novel.  According to a news item in HR in August 1933, Fred Niblo, Jr. and C. Gardner Sullivan were collaborating on a screenplay for Operator 13, but the extent of their participation in the completed film has not been determined.

According to various news items in DV and HR, production began on February 1, 1934 under Walter Wanger's supervision and Raoul Walsh's direction, with Al Shenberg working as the assistant director.  On February 12, 1934, production was stopped on orders from William Randolph Hearst, the head of Cosmopolitan Pictures.  A DV news item notes that all of the film shot was scrapped and a new story was written.  At that time, Wanger was replaced by Lucien Hubbard, who was originally intended to produce the picture.  Because Walsh protested the new script, he was also taken off the film.  The picture resumed production on February 19, 1934, under Hubbard's supervision, with Richard Boleslavsky the new director and Red Golden the new assistant director.

Although the CBSC lists Jay Lloyd as "Gaston," Wade Boteler is credited with that role on the film.  Var commented, "Miss Davies is particularly effective as a colored wench, a disguise she simulates in one major chapter as the maid to Katherine Alexander.  Her dialect and mannerisms are decidedly effective."  For his work on the film, cinematographer George Folsey received an Academy Award nomination.

Music includes:  "The Colonel, Major and the Captain," "Once in a Lifetime" and "Sleepy Head," words and music by Walter Donaldson and Gus Kahn; "Jungle Fever," words and music by Walter Donaldson and Howard Dietz.