Written in Draconic, found tucked into the violin discovered in Chapter 2:
For Erich, don’t forget.
In Chapter 6, it was revealed that this note was written in Dora’s hand.
In Chapter 87, Dora learned that she and Thema have different handwriting, which means that Dora wrote the note some time before she woke up in Briarstone Asylum.
In Act IV, Interlude Part 1, it was revealed that Stanhope took the violin from Dora while she was sleeping because he believed she had deliberately left it to him as a gift (owing to his own middle name being Erich).
First Reference: Chapter 2
Other Notable References: Chapter 6, Chapter 87, Act IV Interlude Part 1