We'll never know who Bruce Partington was, but his plans for a secret submarine are the sole concern of this episode. Holmes becomes a submarine expert, Mycroft is bestirred from his usual rounds, and absolutely nothing is as it seems apart from oysters being in season.

A cartography aficianado, a Spanish visitor (because we can't have an ACD story without the othering of the...other), and a rather sinister Inspector Baynes - and a spirited pair of children - bring Holmes and Watson to Surrey, where they have to solve a distinctly Iberian mystery.

A prominent raceshorse with a magnificent pedigree is missing. His trainer is dead. And...a guard dog didn't bark. The curious incident of the dog in the nighttime provides the essential clue that allows Holmes and Watson to solve the case.

Holmes is supposedly on vacation for his health - but he and Watson are interrupted by a vicar who is concerned about his parishoner Tregennis, who'd been playing cards with his siblings and then arrived the next morning to encounter them all dead or crazed. Is it poison? Or is it poison?

We're racing along Holmes and Watson as they follow Very Good Dog Toby along the Thames. A very slow so-called high-speed race and a mudbath later, and we are back at 221B, where after copious amounts of whisky, Jonathan Small (aka John Thaw, aka Endeavor Morse) tells everyone how he came by the fortune and what he's done with it.

Holmes and Watson are summoned to help Miss Mary Morstan, who has been apparently deprived of a great fortune. But what do Henry Irving, Oscar Wilde, and Bram Stoker have to do with any of it? Turns out...everything.

Five little busts of Napoleon have been stolen and smashed. Is it an obsession with the depredations of the Bonaparte campaign through Europe? It was a package of six - where is the final statuette? And how can Holmes and Watson solve this mystery?

A missing opium addict leads Holmes and Watson to another case missing persons case entirely - that of Neville St. Clair, a businessman who goes to London every day for work. But one day his wife spots him in the upper window of an opium den - and then he disappears completely, leaving behind only his overcoat, which is stuffed with loose change. An enormous yellow sponge proves the tool to solve the case.

Sir Eustace Brackenstall has been murdered, and Holmes and Watson rush to the crime scene. But all is not as it seems. A bell-pull, some empty glasses of port, and a "multiplex" tool (who knew they had Swiss army knives back in the day) with a corkscrew in it prove to be the deciding factors in what would be a locked room mystery...were it not for the open window.

Holmes - somewhat reluctantly, and incidentally on drugs - takes Watson to visit his old school acquaintance Reginald Musgrave, the scion of one of the oldest families in Sussex. Musgrave's butler has been acting very strangely, and there's an ancient document - a ritual - that has haunted the family since the 17th Century. Can Holmes and Watson solve the case? Of course they can - that's a given. But what else is entailed? That's the fun part.