Why Bother to Knock (1961)

Bill Ferguson, who owns his own travel agency in Edinburgh, is hoping that after two years of dating, he and girlfriend Stella Napier will move their somewhat stalled relationship to the next level of being engaged. Instead, partly due to an issue stemming from he losing his apartment key, she breaks up with him. Needing a distraction to mend his broken heart, Bill take an extended business trip to the continent. It is on that trip that in finding that Stella has gotten engaged to another man, Bill ends up reconciling with Stella, they getting engaged themselves. Complications ensue stemming from a bon voyage gift given to him from American friend and client Maggie Shoemaker before he left for the continent in her want to help him get over Stella and find true love: several duplicates of his found apartment key to give away to the plethora of mesdemoiselles, frauleins, and senoritas he romances on his trip. The problem is that three of those women with said keys end up showing up at his apartment in Edinburgh, he needing to hide the true nature of their relationships with him from each other and more importantly Stella, while he can only admit to himself and to Maggie that he'd really like to have his cake and eat it too especially with one, Lucille Daumier.