Move over, Sherlock Holmes!Drusilla is a quiet, thoughtful little girl who has a small toy hippopotamus and four older brothers.

Her hippo (Mrs Mu) goes everywhere with Drusilla. Her brothers (Harlan, Kal, CJ and Joe) go nowhere with her.

In fact, their sole aim seems to be to taunt their small sister and stop her from joining in with their games.

Usually Drusilla can withstand any amount of teasing, but when Mrs Mu goes missing, she suspects foul play… This time Drusilla will have to call upon all her resourcefulness to win through.