Murder at the Masquerade. Cassie Pengear Mysteries, #13

When Cassie Pengear's cousin Milly invites her to a masquerade ball at the Melpomene Theatre, her first instinct is to say no. The last party Milly had invited her to ended in murder, and these tickets came from one of Milly's gentlemen callers, never a good sign. But dressing up for a Halloween masquerade at a theater did sound fun, so she agrees. And the masquerade is fun, until someone discovers a body.
With Inspector Burrows in charge, Cassie figures the case is in good hands and out of hers, until Milly drags them into investigating the murder at the masquerade. In a Victorian England that almost existed, a steampunk London where tinkerers and clockwork devices exist alongside hansom cabs and corsets, murder is still solved by traditional observation and intuition. This is the London where American typist Cassandra Pengear finds herself stumbling over corpses and helping Scotland Yard detectives solve murders (although they inexplicably prefer to call it interfering).
Follow her adventures in the Cassie Pengear Mystery series, beginning with The Killing at the Carnival.