It is Harou´ (yes, there's that unusual accent, but it is not always used in period print ads). There was a discussion of this label in a private forum, and one of the clips found by a member read:
"Not yet in his class is William Pearson, also a designer of talent. Mr. Pearson has had his own business for six of his 36 years before that working for Harou, a California concern. His clothes have a young, contemporary look." (1966) So, Pearson designed for Harou´—I wish I could help with more.
I believe the earliest clipping posted was 1959, and others dated from the 60s. I'll bet your dress is great, because all I've seen by this label have been very impressive!