Deanna Durbin and director Charles David were wed in 1950 and retired to a life in rural France. They remained married until his death in 1999.
Deanna mêne l'enquête (1945) is adapted from the same short story by Leslie Charteris that provides the basis for Signal Stop (1978) from the series Le retour du Saint (1978), about Simon Templar, a character Charteris created. According to Robert S. Baker, the executive producer of "Return of the Saint", Charteris was surprised by the similarity of Signal Stop to Lady on a Train. Whether John Kruse had seen the latter film prior to writing Signal Stop is unknown.
Despite singing three songs, this is a rare non-musical movie role for Deanna Durbin, who had been one of Universal Pictures' biggest box office stars in the late 1930s and early 1940s. It was produced as a vehicle to propel her career.
Since audiences expected to hear Deanna Durbin sing in her films, the screenwriters had to work at least a handful of singing opportunities into this film's faux murder mystery plot. At one point, they resort to having Durbin's character sing an extensive a capella version of "Silent Night" over the phone to her father on Christmas Eve.