"The Adventure of the Oft-Adapted Detective": Adaptations of Sherlock Holmes by LeiA

Question 1

In the 1945 film, "Pursuit to Algiers", one of many films starring Basil Rathbone and Nigel Bruce as the original dynamic duo, Dr. Watson regales the passengers of a cruise ship with a tale about what creature tantalizingly mentioned in "Adventure of the Sussex Vampire"?

Giant Rat of Sumatra