The boxes once belonging to Doctor Watson containing notes related to cases and adventures of his friend, Sherlock Holmes, are still not empty. Here we find five such adventures, four of which are mentioned in the original collections published through Watson's literary agent, Sir Arthur Conan Doyle, and brought together here.

• The Adventure of the Broken Door is mentioned briefly (but not by that name), in The Norwood Builder.
• The Adventure of the Green Dragon has an oriental flavour and is referenced (though the reference is obscure) in The Cardboard Box.
• The Adventure of John Vincent Harden is mentioned in by name in the Solitary Cyclist.
• The Adventure of the Copper Pins is mentioned (but not by that name) in The Five Orange Pips.
• The Adventure of the Deceased Doctor is unusual, as it occurs some two and half years after His Last Bow, when Holmes and Watson are both serving their country in the Great War.