In early 1947, Screen Guild Productions experimented with a new format: a 90-minute double feature package, consisting of two simultaneously-filmed 45-minute mysteries. As it turned out, The Hat Box Mystery and The Case of the Baby Sitter were released separately, within two weeks of one another. Both films starred Tom Neal as a private detective named Russ and Pamela Blake as his secretary Susan, both were cowritten by Carl K. Hittelman, and both were directed by the prolific Lambert Hillyer. In
Hat Box Mystery, Russ comes to Susan's rescue when she's accused of murdering one of their clients. Per the title, the main clue is a sawed-off shotgun, hidden in a hatbox-a gimmick reportedly inspired by a real-life murder case. Allen Jenkins provides some laughs as a near-illiterate goofball inappropriately named Harvard. ~ Hal Erickson, All Movie Guide