Nor was he an expert on duelling.

It must have been Kate.
Yes--of course--it was Kate and her treatment of him.

The "tide" was what had swept them apart.
"Oh, I know," he cried in an animated tone.

"He meant Kate.

Tell me--what did he say about her ?" He had searched his books for some parallel from which to draw a conclusion, but none of them had given him any relief.