This cabinet card portrait features a young man and woman posing for their portrait at the Stewart studio in Scranton, Pennsylvania. Presumably, the couple are husband and wife. This is an interesting and unusual photograph. Note the man’s facial expression as he stares at his wife. I have been struggling to find the precise words to interpret his countenance. The best way that I could describe his expression is “incredulous bemusement”. He is looking at his wife out of the corner of his eye and seems amazed. I see no intimacy between this marital pair. They appear entirely disconnected. The woman’s feathered hat is on the floor in front of the couple. Interestingly, the man’s hat is given better treatment than the woman’s hat. The woman is holding her husband’s hat and keeping it off the dirty ground. The idea that she has to be the keeper of her spouse’s hat seems a bit subservient. However, we have to remember that this photograph was taken over one hundred years ago and gender roles were far different that they “generally” are today. SOLD
THE CABINET CARD GALLERY 
Your description of the husband’s expression is spot on. But I interpret the rest of this scenario differently. I see her discarding her hat for his as a bold move on her part, asserting who is boss. He admires this spunkiness in her, but his face reveals a bit of doubt.
Your interpretation can certainly be correct, as can mine. I think that is part of what Makes these cabinet cards so interesting. Developing these explanations for what is going on in the photographs allow us to use our detective skills and our imagination.
The mystery is a main reason I visit here — to see what others think as well as offer my own ruminations.
I don’t think he was looking at her. Perhaps his look was directed to the photographer. Perhaps she was female. LOL!