“Well, there is a chance of it, anyhow,” amended Poirot. “Also, I learn that a swarthy man, a foreigner of some kind, was inquiring about the occupants of No. 4 only this morning. Therefore, mon ami , I fear that you must forswear your beauty sleep tonight, and join me in my all-night vigil in the flat below⁠—armed with that excellent revolver of yours, bien entendu !”

“Rather,” I cried with enthusiasm. “When shall we start?”

“The hour of midnight is both solemn and suitable, I fancy. Nothing is likely to occur before then.”