The Evil Shepherd by E. Phillips Oppenheim

It was one of those faultless June evenings when the only mission of the faintly stirring breeze seems to be to carry perfumes from garden to garden and to make the lightest of music amongst the rustling leaves. The dinner-table had been set out of doors, underneath the odorous cedar-tree. Above, the sky was an arc of the deepest blue through which the web of stars had scarcely yet found its way. Every now and then came the sound of the splash of oars from the river; more rarely still, the murmur of light voices as a punt passed up the stream. The little party at The Sanctuary sat over their coffee and liqueurs long after the fall of the first twilight, till the points of their cigarettes glowed like little specks of fire through the enveloping darkness. Conversation had been from the first curiously desultory, edited, in a way, Francis felt, for his benefit. There was an atmosphere about his host and Lady Cynthia, shared in a negative way by Margaret Hilditch, which baffled Francis.

It seemed to establish more than a lack of sympathy -- to suggest, even, a life lived upon a different plane. Yet every now and then their references to everyday happenings were trite enough. Sir Timothy had assailed the recent craze for drugs, a diatribe to which Lady Cynthia had listened in silence for reasons which Francis could surmise.