Porr Catherine ,caught out snooping......

With a feeling of terror not very definable, she fixed her eyes on the staircase, and in a few moments it gave Henry to her view. “Mr. Tilney!” she exclaimed in a voice of more than common astonishment. He looked astonished too. “Good God!” she continued, not attending to his address. “How came you here? How came you up that staircase?”

“How came I up that staircase!” he replied, greatly surprised. “Because it is my nearest way from the stable–yard to my own chamber; and why should I not come up it?”

Chapter 24

In teh wonderful book,Stoneleigh Abbey :The House, Its Owners,Its Lands edited by Robert Bearman, there is a fascinating chapter by Gaye King , entitled The Jane Austen Connection

Do take a look at this snippet from it:

Henry Tilney put thoughts of the dreadful possibilities she might find to match her imagination,stirred as it was by the gothic novels she had been reading.

She decides that the cruel General Tilney had done something dreadful to his wife. As soon as she could steal away on her own, she went in search of Mrs Tilney's bedchamber, which had been left as it was when she died.

Following her route as set out in the novel, we find it coincides nicely with Mrs Austen's descritpion of teh " alarming aprtment".No sooner theree than Catherien hears footsteps from an unexpected direction.Looking for an escape she finds herself at teh head of some stairs whihc lead to a long galllery.Here Herny Tilney cathces teh guilty CAtherinand immediately understands her quest.

He can more easily explain his own presence at that spot.

This was the easiet route to ihs quarters.

Acccording to old drawings , we can locate the stable at Stoneleigh,where , in Jane's imagination, he(HT_JW) would have left his horse, and the old steps leading from the north front into the gallery. Had he come through the ground floor entrance , he would have come up a flight of stairs at the end of the connecting pasage, now marked bya anrrow , ornate door, up to teh gallery outside the door of the alarming apartment.

Stoenleigh having turned bout to be an Abbey, the lively mind of the novelist was entertinaed by placing there a delightful set of characters she ahd created from an earlier novel
pp175-6

..Interesting , don't you think, that Henry's back stairs can be located on old plans of Stoneleigh ;-)