Hmm...sounds like Cressida's forcing them to come.
Can't wait for the conclusion!

P.S. This was my favoritest part thus far:
"For good reason. One eccentric in a family is just tolerable--a dozen is absolutely unbearable."
Mycroft glanced at me and raised his brows, indicating his brother with his eyes. I hurriedly turned my laugh into a cough when Holmes glared.