Los Angeles policewoman Madeleine Haley is assigned by the police department to uncover evidence against narcotics smuggler Pete Richie. Disguised as a blowzy chorus girl named Gladys La Rue, Madeleine gets a job in a Mexican nightclub frequented by Richie. During the show, she unsuccessfully tries to attract his attention. Later, she makes a play for Deusik, one of Richie's men. After he gets drunk, she helps him back to his room and when he passes out, searches the place. While she is searching the bedroom, Richie enters. She is able to convince him that she was just "freshening up," and he asks her to stay. Suddenly, Johnny Macklin, who works for rival smuggler Harvey Gumbin, breaks into the room and demands information from Richie. When Richie is not forthcoming, Macklin tortures Deusik. A fight breaks out, and Madeleine is forced to shoot Richie in self-defense. Macklin then leaves, taking Madeleine, whom he believes to be Richie's girl friend, with him. Later, Gumbin sends her and Macklin on a dope smuggling run, posing as a honeymooning couple. That night, when they are stopped at a hotel, Macklin and the driver, Miguel, go out for supplies, and Madeleine photographs their fingerprints. Meanwhile, Macklin sends a telegram to the Customs Office, for which he is working undercover, and later photographs Madeleine's fingerprints. In the middle of the night, Richie and his men arrive, bent on revenge. Madeline and Macklin manage to evade Richie, who then lays an ambush for them farther up the road. With the help of some quick thinking by Madeleine, they escape the trap, but Miguel is killed. They abandon their car and get a ride with Porfirio, a farmer, who is also the local sheriff. Meanwhile, the police discover Miguel's body and the abandoned car, and only some fast work by Madeleine forestalls their arrest. Porfirio arranges for a friend to fly Macklin and Madeleine to Ensenada. On the way, they run out of gas and are forced to spend the night on the beach. By morning, Macklin and Madeleine have fallen in love. They finally arrive in Ensenada and are scheduled to cross the border the following day. Each thinks this means he will have to turn the other over to the police. Richie also shows up, and Macklin plots with his contacts to arrest him. After Richie is arrested, Macklin and Madeleine reach the border, where Madeleine is arrested. When she identifies herself as a police officer, however, no one believes her. She then learns that Macklin is a government agent. Finally, Whittaker, Madeleine's boss, arrives and confirms her story. He orders Macklin and Madeleine, who are now both mad at each other, to continue their ruse and meet their contact at the Los Angeles zoo. To Macklin's surprise, Gumbin is revealed to be the head of the operation. They all meet later at Gumbin's house and after a shootout, the smugglers are arrested. Madeleine expresses her relief that Macklin is safe by giving him a big hug.