She was a girl who could command the gift of coronets.

With restoration to her father and home, gratitude to her preserver would assuredly remain, but, alas! love might vanish like a mirage.

Then he would act honorably.

Half of the stored wealth would be hers to do as she chose with it.
Yes, this was a possible alternative.

In case of accident to himself, and her ultimate escape, he must immediately write full details of his discovery, and entrust the document to her, to be opened only after his death or six months after their release.
The idea possessed him so thoroughly that he could brook no delay.