Task: Question Generation
Input (English): Context : Arthur, the Piper, and Superior Saturday all receive messages from Lady Friday, saying she has abdicated the rule of the Middle House and that the first of the three who can reach her Scriptorium in the Middle House can claim the Fifth Key and her domain as their own. 
Subject : Lady Friday 
Relation : series
Output (English): What is the series that Lady Friday is a part of?