sentence: other arthur conan doyle short stories apart from '' the adventure of the empty house '' , the episode contains allusions to many other doyle short stories : sherlock calls lord moran by the code name '' giant rat of sumatra road '' because of his status as mole for north korea , a reference to '' the giant rat of sumatra '' mentioned in passing in '' the adventure of the sussex vampire '' and because moran 's planned terrorist attack involves an abandoned section of the london underground system called '' sumatra road '' .