The Case of the Gypsy Good-Bye (Enola Holmes, #6)2010
by Nancy Springer
As Enola searches for the missing Lady Blanchefleur del Campo, she discovers that her brother Sherlock is just as diligently searching for Enola herself--and this time he really needs to catch her! He is in possession of a most peculiar package, a message from their long-lost mother that only Enola can decipher. Sherlock, along with their fastidious brother Mycroft, must follow Enola into the reeking tunnels of London's dark underbelly as they solve a triple mystery: What has happened to their mother? And to Lady Blanchefleur? And what does either have to do with Mycroft, who holds Enola's future in his ever-so-proper hands?
No one, not even Sherlock, is left unchanged or unsurprised in this brilliant conclusion to the Enola Holmes mystery series.