Mr. Grex of Monte Carlo is a 1915 spy novel by the British writer E. Phillips Oppenheim.

[1] The action takes place in Monaco, a favourite setting in the author's novels.

[2] Oppenheim was a pioneer of the modern spy genre, often giving his works a glamorous international setting.

[3] The same year it was made into an American silent film of the same title directed by Frank Reicher and starring Theodore Roberts, Dorothy Davenport and Carlyle Blackwell.

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