Pre-production on the film began in early February 1945, more than two years before its release. Thalia Bell of "Motion Picture Daily" and Irving Spear for "Boxoffice" reported then that RKO had hired author Steve Fisher to begin writing the screenplay for James Gunn's 1943 novel "Deadlier Than the Male". By April, however, the studio had replaced Fisher and enlisted freelance screenwriter Eve Greene and later Richard Macaulay to compose the script as a team and to manage its editing through production.