I give the devil his due.
"All this distresses you, dear.

But I cannot help it; you would have to know, sometime, that Colonel Arran and I are enemies.

So let it go at that; only, remembering it, avoid always any uncomfortable situation which must result in this man and myself meeting under your roof." His letter ended in lighter vein--a gay message to Celia, a cordial one to Letty, and the significant remark that he expected to see her very soon.
The next night he tried to run the guard, and failed.
She had written to him, begging him not to; urging the observance of discipline, while deploring their separation--a sweet, confused letter, breathing in every line her solicitation for him, her new faith and renewed trust in him.
Concerning what he had told her about his personal relations with Colonel Arran she had remained silent--was too unhappy and astonished to reply.

Thinking of it later, it recalled to her mind Celia's studied avoidance of any topic in which Colonel Arran figured.

She did not make any mental connection between Celia's dislike for the man and Berkley's--the coincidence merely made her doubly unhappy.
And, one afternoon when Letty was on duty and she and Celia were busy with their mending in Celia's room, she thought about Berkley's letter and his enmity, and remembered Celia's silent aversion at the same moment.
"Celia," she said, looking up, "would you mind telling me what it is that you dislike about my old and very dear friend, Colonel Arran ?" Celia continued her needlework for a few moments.