In chapter eleven, Doctor Watson mentions a box found in the river Thames. Did you know that a box was, actually, found in the Thames but in 2013? And not the kind of box you would expect- no, it was a post box. I just found that fascinating. Another strange object found in the Thames was a young bottlenose whale. Other strange objects include body parts, a time bomb (this link leads to a top ten list) , a zulu spearhead (another list of artefacts discovered in the Thames) and a prisoner's ball and chain.
In chapter twelve, we also discover the box is empty. Of course, Small has made off with the loot, but a real life example of an empty treasure chest can be found here, after an Indian archaelogy expedition turned up a treasure chest only to reveal it was emptied years previous, under "mysterious" circumstances.
And, of course, everyone can relate to Holmes' plight towards the end as his life-long friend and constant companion leaves him for a woman he has come to love in this short time, leaving Holmes feeling lonely and forgotten (and somewhat indignant). Remember, though, that despite John is leaving with Mary, adventures with the dynamic duo will continue on- they are soulmates, after all (how you take that is up to you). -KATIE
(picture is a link to OP's DeviantArt)