First appearance of recurring character Detective Inspector Jack Grace.
When Lizzie and the others joke that 'Lizzie' is only a nickname, after Lizzie Borden, and she asks to be given back her axe - this is in reference to a well-publicized murder case in the USA dating to 1892-3 wherein Lizzie Andrew Borden was tried and acquitted of the axe murders of her father and stepmother. She died in 1927.