The project initially was proposed as a TV series but was retooled as a film after the plot seemed to be going nowhere.
When promoting his program The Loudest Voice (2019) on the Howard Stern Show, Russell Crowe said this was one of two films where he wishes there was a sequel as he liked playing the character; the other was L.A. Confidential (1997).
The book Holly reads aloud from ("Had Mademoiselle Blanche been in England before? What part of France did she come from?") is Cat Among the Pigeons (1959) by Agatha Christie.
Russell Crowe put on some extra weight for the role of Jackson Healy, feeling the character, as an enforcer thug, should be a "stocky brawler type."
One of the film's nods to The Rockford Files (1974) is the yellow pages ad for Holland March's detective agency. It is almost a complete copy of the ad used for Jim Rockford. Like Rockford, March keeps his gun in a cookie jar.