She also had received a whiff of the sweet, heavy gas which had been used, that seemed now to be tincturing the whole atmosphere of the car, especially in the long narrow passage.

It was not likely they intended to kill the man, for his death would cause an awkward investigation, while his statement that he had been rendered insensible might easily be denied.
As she sat there, the silence disturbed only by the low, soothing rumble of the train, she heard the ring of the metal cylinder against the woodwork of the next compartment.

The men were evidently removing their apparatus.

A little later the train slowed, finally coming to a standstill, and looking out of the window into the darkness, she found they were stopping at an ill-lighted country station.

Covering the light in the ceiling again, the better to see outside, herself, unobserved, she noted the conductor and another man place the bulky cylinder on the platform, without the slightest effort at concealment.