Holmes asks a series of follow-up questions, especially regarding the footprints. He wants to know how many dogs are on the moor generally. Mortimer responds that there are a great many, generally large sheep dogs used in farming. These prints, however, were from an even larger dog.
The Old English Sheepdog is an impressively large dog, weighing up to 100 pounds. However, the dog’s long, mop-like coat coupled with its typically bubbly attitude means that it’s far from intimidating.
Knowing Mortimer to be a man dedicated to science and medicine, Holmes is taken aback that the doctor seems to believe that a supernatural hound had something to do with the death. Mortimer responds that he doesn’t know what to believe, but that his neighbors have all reported seeing a spectral hound with glowing eyes and mouth stalking the moors.
Flippantly, Holmes responds that he has often combated evil through his work as a detective, but that combating an actual agent of the devil might be a bit out of his league. He reminds Mortimer, however, that the hound is leaving behind an awful lot of physical evidence, such as footprints, for something supposedly supernatural.
The rules for how a supernatural being would interact with the natural world aren’t readily apparent. For instance, it’s not clear how the supposedly supernatural hound would harm Sir Charles—aside from giving him a heart attack—if it were unable to do so much as leave footprints in the dirt.
Holmes asks Mortimer why he would consult him at all, if the doctor really believes that Sir Charles’ death was brought on by a hound from Hell. If this is true, after all, there’s nothing to be done about it. Mortimer replies that he doesn’t want Holmes to investigate Sir Charles’ death. Rather, he wants Holmes to advise him regarding Sir Henry Baskerville’s coming arrival.
Monstrous dogs from the afterlife have appeared in literature since at least Cerberus, the three-headed dog of Greek mythology who made sure that departed souls stayed in the underworld. A similar creature—albeit more horse-like—appears in Charlotte Brontë’s Jane Eyre.
Mortimer is worried that whatever happened to Sir Charles will shortly happen to Sir Henry if the young Baskerville is allowed to simply move into Baskerville Hall. Mortimer confirms that Sir Henry is the last surviving Baskerville, largely because every Baskerville who has gone to the Hall has met an evil fate.
The allure to return to the “home of one’s fathers” is seemingly so strong that it overrides common sense. If Baskervilles die when they go there, then the obvious solution seems to be for Baskervilles to simply not go there.
Holmes asks Mortimer to bring Sir Henry to the Baker Street apartment the next day. In the meantime, Holmes will ponder the case. He chooses to do this by confining himself in the apartment and smoking until the air becomes so thick that breathing becomes difficult. This, he tells Watson, helps him to think.
With the available data, Holmes comes to only one conclusion. Sir Charles was terribly afraid of the moors and avoided them at all costs, especially at night. If he was killed in the evening, by the moors, it’s because he intended to meet someone there.
Any number of things might have caused Sir Charles to approach the moor that night, but following his performance with Mortimer’s stick, Holmes is allowed some shaky inferences.