She had been wondering how she could get at Mr.
Ryder and here he was actually asking her to call on him.
Evidently he had not the slightest idea of her identity, for he had been able to reach her only through her publishers and no doubt he had exhausted every other means of discovering her address.

The more she pondered over it the more she began to see in this invitation a way of helping her father.

Yes, she would go and beard the lion in his den, but she would not go to his office.
She would accept the invitation only on condition that the interview took place in the Ryder mansion where undoubtedly the letters would be found.

She decided to act immediately.

No time was to be lost, so she procured a sheet of paper and an envelope and wrote as follows: MR.