What a coincidence Cary Grant was in Switzerland

I felt as soon as he found out about the murder he discovered her travel plans and went to see her before she even knew about the murder.

The two meet in Megeve, which is in the alpine region of France.

As Grant's character worked for the Treasury Department, he was aware of the key players involved in the original theft and knew that three of them had finally caught up with Charles Lampert. And since there's every indication he's already in cahoots with Tex, Gideon & Scobie (passing himself off as Carson Dyle's brother), it makes perfect sense he'd be in Megeve; the four had undoubtedly decided one of them should "accidentally" meet Regina to discover how much she knows about the money and its whereabouts. I'm sure it didn't take them long to figure out she'd be most likely to put her trust in Cary Grant's suave, sophisticated character.

I think the movie makes all of this clear; however, there's a lot of detail to sift through, and all the plot twists may not be immediately apparent after a single viewing.