The So Blue Marble is a 1940 mystery thriller novel by the American writer Dorothy B.

[2] The manuscript was trimmed by 25,000 words at the demand of the book's editor, establishing the author's terse, hard-boiled style.

One night she is accosted by two handsome, well-bred but ruthless twins recently arrived from Europe.

They turn out to have Missy, Griselda's much younger sister, who she hasn't seen for many years, in tow.

They insists that Griselda has it, and are prepared to commit multiple murders to get their hands on it.