When wealthy Mr. Ames is murdered, his beautiful wife Hope (Madeleine Carroll) is the principal suspect. She is acquitted through lack of evidence, but it's hardly a happy ending: her son Bobbie (Scotty Beckett) is taken away from her by spiteful relatives, who poison the boy's mind against her. Making matters worse, assistant DA Matt Logan (George Brent) is still convinced that Hope is guilty. Upon seeing Hope's devotion to her child, Logan softens a bit and alters his strategy. He offers a huge reward for additional information pertaining to the case, ostensibly to prove Mrs. Ames' guilt, but actually to clear her name so that she and her son can be reunited. If the outcome of The Case Against Mrs. Ames seems predictable, it is only because the actor who plays the real murderer was nearly always revealed as the "surprise" culprit in the final reel.
by Hal Erickson synopsis