«Emily Gray and the Resurrection Men» by R.W. Kent

Set in London in the early 1800s, ‘Emily Gray and the Resurrection Men’ begins when Emily wakes in a coffin where she’s been buried alive. She’s rescued by grave robbers — or Resurrection Men, as they prefer to be called — and Mister Crawley and Mister Spratt promise to help Emily get back home.
However, Emily has lost her memory due to her terrifying, traumatic experience. There are only three clues to Emily’s past: she has an intricately engraved locket, containing portraits of who she assumes are her parents; she finds a strangely-marked bee, dead, tangled in her hair; and she has recurring dreams of a gaping tunnel entrance marked with the roman numerals XII.
Emily, Mister Crawley and Mister Spratt embark on a journey around the grimy streets of Regency London seeking help from a variety of characters, chief among them the ruthless Gabriel Grubb, the leader of a vicious gang of criminals; the strange old crone Mrs Tattershall, who discerns something dark in Emily; and, in the London Docks, the Persian warehouse owner Bhaktavar.
Emily soon realises that finding her parents won't be easy — and that her forgotten past might have been more harrowing than she could ever have imagined.