Always liked Marion Davies in most of her films. She always played good-natured, cheerful parts in which you can root for her character. But I guess everyone's entitled to a clinker once in a while, and I thought "Operator 13" is hers. She is hard to believe as a Northern spy in blackface - she doesn't look like a black person at all, and in real life would fool no one. Her makeup as a white spy looks laid on with a trowel, and in addition she doesn't sing well when called upon.
The plot itself is a good one and is handled well by underrated director Boleslawski, who died too soon. The scenes of intrigue and espionage are very good, as are the few fight and battle scenes, but the picture goes downhill in the love scenes between Davies and Gary Cooper. The dialogue here seems forced and Davies tries too hard to play an ardent lover. Rest of the cast is excellent with several recognizable character actors, including Ted Healy (minus the 3 Stooges) as a Union Captain.