The Colossus of Arcadia is a 1938 spy thriller novel by the British writer E. Phillips Oppenheim.

[1] Oppenheim enjoyed great popularity in the interwar era for his series of thrillers, often concerning international intrigue.

[2] Set in Monaco, a frequent location in the author's novels, it uses passengers arriving and then departing on the Blue Train for its opening and closing chapters.

[3] A variety of travellers arrive in Monte Carlo under the shadow of an expected war between France and Germany.

One of them is the heir to a large German banking firm and is under pressure to return to his native country.