A caravan settles for the night in the Gobi Desert. A man sneaks into a tent to steal a scroll, but adventurer and soldier of fortune Kentaro Moto (Peter Lorre) is only pretending to be asleep and kills him. When the caravan reaches Peiping, Moto is searched by the police. The scroll is found, but Moto grabs it and escapes.
He changes clothes and accepts an invitation to a party hosted by Colonel Tchernov (Sig Ruman) in honor of American Eleanor Joyce (Jayne Regan). At the soirée, Moto observes a guest, Chinese Prince Chung (Philip Ahn) leaving his mother to speak privately with Tchernov in another room. Tchernov offers to buy certain family heirloom scrolls from Chung. When Chung refuses to part with them, Tchernov draws a pistol, then is killed (off-screen) by Moto. Joyce stumbles upon the scene and watches in disbelief as Moto calmly stages it to look like a suicide. Moto politely advises her to say nothing to avoid an international incident.
Later, as a favor to his rescuer, Chung grants Moto's request to see the scrolls. Chung informs him that the seven scrolls give directions to the lost grave of Genghis Khan. The Chungs are determined to see that it and its fabulous treasures remain undisturbed. However, one scroll was lent to an exhibition and was stolen.
A dealer in antiquities, Pereira (John Carradine), shows Joyce some wares. She is interested in a (fake) scroll, but the price is too high. While shopping the next day with smitten diplomat Tom Nelson (Thomas Beck), they see Moto entering Pereira's shop. Moto gets Pereira to confess that he stole the authentic scroll, but before he can obtain more information, Pereira is shot and killed by a gunman in a car which speeds away.
Moto returns to his apartment to find it ransacked. Sensing that the would-be thief is present, Moto leaves his gun lying around. Schneider (Wilhelm von Brincken) holds him at gunpoint and forces Moto to give him the scroll. When Moto tries to flee, Schneider shoots several times with Moto's gun. However, the gun was filled with blanks; Moto trails Schneider to Madame Tchernov (Nedda Harrigan). When they leave to rendezvous with their gang, Moto starts to follow, but is knocked out by the butler, Ivan (John Bleifer), another crook. Joyce, who had been comforting the widow, is taken hostage.
The arch-villain (and Madame Tchernov's lover), Herr Koerger (Sidney Blackmer), forces Prince Chung to reveal the location of the scrolls by striking his mother. As they are leaving, Madame Chung attacks Koerger with a knife and is killed. Meanwhile, Nelson finds and revives Moto. They rush to the Chungs, but arrive too late. The dishonored prince commits suicide after they untie him; Moto comforts him before he dies by promising to avenge the Chung family and safeguard the tomb.
The two men track the criminals to a junk. After another attempt to kill him, Moto informs Koerger that the scroll he gave Schneider is a fake. He offers to split Genghis Khan's treasure. Then he sows dissent by telling Madame Tchernov that Koerger is dumping her for Joyce, which the quick-thinking American "confirms". This provides a distraction for Moto to kill Koerger. Later, to the dismay of Joyce and Nelson, Mr. Moto burns the scrolls to fulfill his promise to Chung.Peter Lorre as Mr. Kentaro Moto
Thomas Beck as Tom Nelson
Pauline Frederick as Madame Chung
Jayne Regan as Eleanor Joyce
Sidney Blackmer as Herr Koerger
Sig Ruman as Colonel Tchernov
John Carradine as Pereira
Wilhelm von Brincken as Schneider (as William Von Brincken)
Nedda Harrigan as Madame Tchernov
Philip Ahn as Prince Chung
John Bleifer as Ivan
Thank You, Mr Moto was the second Mr Moto novel following No Exit and was published in 1936 after having been serialised first. The New York Times praised the book's "vitality and vividness".
When it was decided to make a movie series from the Moto books, the first three films were to be Think Fast, Mr Moto, then Thank You, Mr Moto and Mr Moto's Gamble.
Jayne Regan was given her first lead when cast in the film. Filming started October 1937.
The film marked the last screen appearance of Pauline Frederick.
This film, along with Think Fast, Mr. Moto, Mr. Moto Takes a Chance and Mysterious Mr. Moto, was released on DVD in 2006 by 20th Century Fox as part of The Mr. Moto Collection, Volume One.