Titus Groan in particular Lord Sepulchrave's twin sisters, Cora and Clarice Groan. The sisters are not very bright and are power-hungry and resentful, believing that Countess Gertrude holds the position that they rightfully deserve. Steerpike manages to use the twins' ambition for his own ends. He promises them power and influence, and convinces them that they could achieve their goal by burning down Sepulchrave's beloved library. Steerpike prepares meticulously for the act of arson. He arranges for the burning to happen when the entire Groan family and their most important servants are inside the library for a family gathering (Steerpike intentionally failed
Titus Groan to tell the twins that they were invited as well, strengthening their feeling of bitterness towards Sepulchrave and Gertrude). He intends to lock the doors to prevent an escape, and then come through the window and save everyone inside from the fire, appearing as a hero and possibly strengthening his position and granting him more power in the castle. Everything goes according to plan: the entire Groan family (including the Earl and his heir) and most of the retainers are saved. Sourdust, the old Master of Ceremonies, dies of smoke asphyxiation and all the books in the library are destroyed