Houdini had broken his wrist while making the movie in late June and wore a cast for a number of weeks. In most photos taken at that time he is careful to remove the sling and cover up his cast. But not this time. Maybe that's why he doesn't look happy. Ann Forrest, on the other hand, looks lovely.
Houdini's accident was reported in the June 27, 1919 Los Angeles Times, which somewhat downplayed the injury.