“Come upstairs first,” said Nightspore.

The upstairs rooms proved to consist of a library and three bedrooms.  All the windows were tightly closed, and the air was insufferable.  The beds had been slept in, evidently a long time ago, and had never been made since.  The tumbled, discoloured bed linen actually preserved the impressions of the sleepers.  There was no doubt that these impressions were ancient, for all sorts of floating dirt had accumulated on the sheets and coverlets.

“Who could have slept here, do you think?” interrogated Maskull.  “The observatory staff?”

“More likely travellers like ourselves.  They left suddenly.”

Maskull flung the windows wide open in every room he came to, and held his breath until he had done so.  Two of the bedrooms faced the sea; the third, the library, the upward-sloping moorland.  This library was now the only room left unvisited, and unless they discovered signs of recent occupation here Maskull made up his mind to regard the whole business as a gigantic hoax.

But the library, like all the other rooms, was foul with stale air and dust-laden.  Maskull, having flung the window up and down, fell heavily into an armchair and looked disgustedly at his friend.

“Now what is your opinion of Krag?”

Nightspore sat on the edge of the table which stood before the window.  “He may still have left a message for us.”

“What message?  Why?  Do you mean in this room?—­I see no message.”

Nightspore’s eyes wandered about the room, finally seeming to linger upon a glass-fronted wall cupboard, which contained a few old bottles on one of the shelves and nothing else.  Maskull glanced at him and at the cupboard.  Then, without a word, he got up to examine the bottles.

There were four altogether, one of which was larger than the rest.  The smaller ones were about eight inches long.  All were torpedo-shaped, but had flattened bottoms, which enabled them to stand upright.  Two of the smaller ones were empty and unstoppered, the others contained a colourless liquid, and possessed queer-looking, nozzle-like stoppers that were connected by a thin metal rod with a catch halfway down the side of the bottle.  They were labelled, but the labels were yellow with age and the writing was nearly undecipherable.  Maskull carried the filled bottles with him to the table in front of the window, in order to get better light.  Nightspore moved away to make room for him.

He now made out on the larger bottle the words “Solar Back Rays”; and on the other one, after some doubt, he thought that he could distinguish something like “Arcturian Back Rays.”

He looked up, to stare curiously at his friend.  “Have you been here before, Nightspore?”

“I guessed Krag would leave a message.”

“Well, I don’t know—­it may be a message, but it means nothing to us, or at all events to me.  What are ’back rays’?”