Seems the son was something of a high-roller, and the old lady knew he'd blow it in, if it was turned over to him without any ballast, like; and the girl was supposed to be the ballast, to hold him steady.

So the old lady, or else it was the girl, writes to this fellow, and he agrees to hook up with the lady and take the money and behave himself.

Near as I could make it out, the time was just about up before the girl took matters into her own hand, and come out on a hunt for this Frank Cameron.

How she happened to sink her rope on you instead, and take her turns before she found out her mistake, you'll have to ask her--if you ever see her again.
"But this much you told me--and I think you got it straight.

The girl was willing to marry you--or Frank Cameron--so he could get what belonged to him.