Luckily, Mary was uncommonly laissez-faire about our plans. She knew we were going to Paris—but she didn’t know where we’d be staying or the agenda. However, when our Uber rolled up to the palatial Le Bristol, she started to get a sense. The hotel, which is celebrating its centennial this year, surpasses every luxury: There are plush robes, private balconies with city views, and lots of champagne.

The next morning, room service rolled into our room with a cart of fruit plates and pastries. I sprung the news: We’d be walking around Paris to try on engagement rings. In one gulp, Mary finished her drink.

But first, another surprise: a manicure at Spa Le Bristol by La Mer. One needs to have their hands in tip-top shape to try on engagement rings, naturally.

Afterwards, we were off. I’d made appointments at five different spots, ranging from small antique boutiques to designer shops to online start-ups with huge stockpiles. Mary had specified that she liked vintage rings—and, critically, did not want a massive diamond like the one we’d seen on the woman at the bar.

Our first appointment was at Osprey, a small shop on Rue Saint-Honoré that sells everything from pearls to opals to gemstones. Inside, there’s a large window of thick glass between the client and jeweler, making it so you must speak with raised voices to hear each other through the glass. Mary described the styles she was interested in, and with a nod, the jeweler went to a back room and returned with three ring boxes. He slid each under a small dip in the glass, like a bank teller. Each ring was pretty, but they all had a setting with a raised stone—something Mary was certain would get caught on her clothes. It was a promising start to the search, but not the place we’d find “the one.”

The next stop on the list was Douze, a chic shop in Saint Germain, where the pieces are simple, tasteful, and elegant. Based on Mary’s reaction to the assortment, it was definitely closer to what she had in mind. Though the pieces aren’t antiques, they’re crafted with a designer’s vision and a similar to the style of jewelry she already owns. We took a business card and left with a new dose of optimism.