Elementary, dear Watson!

In “The Sign of Four", Sherlock Holmes 1 makes some very startling inferences about Watson's whereabouts by informing Wat-son that he was at the Wigmore Street Post Office earlier that morn-ing. On further inquiry by Watson, Holmes explains that he com-bined (joined) the observation that “Watson's shoes had a reddish mud on their instep", with the fact that “just opposite the Wigmore Post Office the pavement was freshly dug up to expose a similar reddish mud and it was so positioned that it would be challenging to enter the ...