Supporting cast
I agree with the observations that this was one too many Thin Man movies and Powell and Loy's interest had cooled. Also the film could have done completely without the kid (somebody, please cut that boy's hair).
But seeing Gloria Grahame and Keenan Wynn made it worthwhile. She needed to put on a few pounds (and did by '50) but even so she was one of the sexiest babes Hollywood ever had.