Be on your guard.

You are in the country of the Borgias." The princess was not a little disturbed by this communication.

Monstrous as was the plot which it purported to disclose, she could not disbelieve it when ascribed to the two men in question.

Certain fearful remembrances of the past confirmed her suspicions, and even inspired her in her distress with thoughts of suicide.
But what if this letter were merely a trap?
Who could have written it?
Who, in that city, where so few knew even of her existence, was sufficiently familiar with her private affairs to be able to write it?
Whom could she now consult, with whom share her anxious forebodings?
Involuntarily she took up her sketch-book, and turned its leaves once more.

In vain; the address was gone--gone with the leaves she had torn out and thrown away in the Colosseum.
Having no further engagements for that morning, she proposed to her companion a second visit to the Colosseum, that she might once more essay the sketch which had baffled her the day before.