The Golden Face by William le Queux

At half-past eight I called for Duperre's wife at the hotel, and she came down wearing a plain, dark-brown motor coat with a small, close-fitting cap to match. She was, indeed, unusually dowdy in appearance.

"Well, George," she exclaimed, as she sat behind me in the car and I drove down Pall Mall, "we're going out on a little adventure, I understand. Do you know where we're going?"