Mardenberg

In the short story The Girl in the Train, Mardenberg is a foreign spy mapping the Portsmouth harbour. His accomplice is called Betty Brighteyes. He is described as a man with a small dark beard and a light overcoat.

Portrayals
In the episode The Girl in the Train of The Agatha Christie Hour, a TV film adaptation of the story, the part of Mardenberg is played by Richard Bartlett. The name "Mardenberg" is not used in the show. Elizabeth calls him the man who looks like "the dear king" (probably meaning King George V). At the end of show, Mardenberg is arrested by the police. This did not happen in the original story.