Housekeeper Mrs. Kunkel learns of the secret vacation by blackmailing the valet. She calls to inform the hotel that the Tobler soap prize winner is really a multi-millionaire and should be treated accordingly, but is interrupted before confirming Tobler's travelling name. Hagedorn is mistaken as the millionaire while Tobler is treated as an unwelcome guest. Gold digging divorcee Mrs. Mallebre (Mary Astor) first tries to woo Hagedorn but soon realizes that Tobler is the real millionaire and shifts her attention to him. Mrs. Kunkel and Tobler's daughter Hilde travel to the resort - Kunkel to rescue Tobler from the gold digger; Hilde to make sure he has a good time. Hilde also hides her wealth and Hagedorn fall in love with her. Their romance is almost spoiled when the deceit is revealed but the whole Tobler household works to patch things up.
Edna May Oliver is incredibly familiar but I'm hard pressed to pick a memorable role. She was in Cimarron but I don't think I've ever seen it. She was the Red Queen in a version of Alice in Wonderland. She was also frequently caricatured in old Looney Tunes cartoons.
Frank Morgan was, of course, The Wizard of Oz.
"Romance for Three" was the UK Title, I guess this was a British print.