Russian refugee Tanya Borisoff [Kay Francis] is suddenly abandoned penniless in Rangoon by her lover, Tony Evans [Ricardo Cortez], when he accepts a gunrunning deal from Nick [Warner Oland], the owner of a sleazy local nightclub. Nick schemes to have Tanya as his main "hostess," and she accepts it after an initial hesitation, hoping to endure a bad situation and survive.
Using the name "Spot White," she becomes notorious for her affairs, which provokes police Commissioner Col. Thomas Dawson [Reginald Owen] to order her deported. She reminds him of a tryst he had with her and extorts 10,000 rupees from him to start a new life. Calling herself "Marjorie Lang," she leaves for Mandalay via river steamer. On board she meets alcoholic Dr. Gregory Burton [Lyle Talbot], who is traveling to assist in an area plagued by a deadly contagious fever.
As Tanya and Dr. Burton begin to fall in love, she learns he's seeking to atone for a past mistake—fatally operating on a patient while drunk. She decides to join him on his medical mission so they can leave their old lives behind and start anew together. But Tony is on the steamer too, and he tries to win her back with feigned love.
Tony receives a wire from Nick informing him that the police are closing in and will arrest him at the next port. He pretends to take poison and jumps overboard, hiding in the boat’s hold. The steamboat Captain finds the evidence and believes Tanya murdered Tony, arresting her. At the urging of Dr. Burton and the first mate, who discovers the wire, the Captain ultimately concludes it was a suicide and releases her.
When Tony later returns to a stunned Tanya, he tries to persuade her to open a club with him in Mandalay, where she could again work as a hostess. Tony’s request pushes Tanya to a decisive act; she notices the poison still in the cabin and quietly slips poison into his drink, handing the glass back to him. Tony drinks and quickly realizes he has been poisoned. Tanya explains that while she has loved him more than anyone else, she cannot return to that life. Tony staggers past her and falls from an open window into the river, unseen by anyone.
The steamboat reaches Mandalay the next morning, and Tanya disembarks with Dr. Burton. As they step onto the pier, Mrs. George Peters [Ruth Donnelly], another passenger Tanya had met earlier, says goodbye. Mrs. Peters, who had already heard of the Captain's decision, remarks that she knew Tanya hadn’t killed Tony, recalling, > "...why I told him (Mrs. Peters' husband) that you wouldn't kill a fly." Walking beside Dr. Burton, Tanya looks ahead with a mix of relief and unresolved emotion.
