1958 was before Ross Hunter embarked Doris Day on the fabulous career she had in the '60s, in which she would become a top box office draw - in fact, THE box office drawer for years. In "The Tunnel of Love," she plays a sweet, vivacious woman who is desperate to have a baby and can't, so she and her husband, played by Richard Widmark, plan to adopt one. When the adopted baby bears a strong resemblance to Widmark, he becomes sure that the child is the result of an evening he can't remember with the investigative social worker (Gia Scala).
Based on a play, this kind of light, subtly sexual comedy became very popular on the dinner theater circuit in the '60s and '70s, joining the ranks of "Mary, Mary", "The Marriage Go Round," "Boeing Boeing," etc. It is not particularly well directed by Gene Kelly and sports the very strange casting of Richard Widmark as Day's confused husband. I can't agree with the comments here. Though an actor known for playing tough roles and cruel men, he does a credible job here mainly because he knows enough not to play for laughs. He creates a full character, that of a caring if foolish man who adores his wife but screws up occasionally. Gig Young plays the philandering husband next door. He's fine, but the character is very unlikable.
There's not really much to recommend here. I suppose at the time it was considered somewhat suggestive, but it doesn't play well today.