The Mystery of the Blue Train by Agatha Christie

Derek Kettering emerged from Van Aldin's suite so precipitantly that he collided with a lady passing across the corridor. He apologised, and she accepted his apologies with a smiling reassurance and passed on, leaving with him a pleasant impression of a soothing personality and rather fine grey eyes.

For all his nonchalance, his interview with his father-in-law had shaken him more than he cared to show. He had a solitary lunch, and after it, frowning to himself a little, he went round to the sumptuous flat that housed the lady known as Mirelle. A trim Frenchwoman received him with smiles.