Lady Meadowcroft looked annoyed.

It would never have occurred to her that within a few weeks she was to owe her life to that very abstruse work, and what Hilda had read in it.
That afternoon, as we watched the flying fish from the ship's side, Hilda said to me abruptly, "My chaperon is an extremely nervous woman." "Nervous about what ?" "About disease, chiefly.

She has the temperament that dreads infection--and therefore catches it." "Why do you think so ?" "Haven't you noticed that she often doubles her thumb under her fingers--folds her fist across it--so--especially when anybody talks about anything alarming?
If the conversation happens to turn on jungle fever, or any subject like that, down goes her thumb instantly, and she clasps her fist over it with a convulsive squeeze.

At the same time, too, her face twitches.

I know what that trick means.