Arthur Conan Doyle · 1890 · thriller

Conan Doyle's second Holmes novel, written for an American magazine over dinner at the Langham. A woman has been receiving a pearl a year from an anonymous sender, and the trail runs from a Norwood villa to a steam launch chase down the Thames - and back thirty years to a treasure taken during the Indian Mutiny.

1. 1
   Baker Street

   Holmes with the cocaine bottle and Watson objecting, and Mary Morstan arriving with a pearl, a letter and a question about her father, who walked out of a London hotel in 1878 and was never seen again.

2. 2
   Pondicherry Lodge

   Thaddeus Sholto's brother is found in his locked garret at Upper Norwood, dead with a thorn behind his ear and the Agra treasure gone - and a bare footprint the size of a child's on the sill.

3. 3
   Lambeth

   Toby the dog follows creosote across south London to a boatyard on the river, and Holmes learns the Aurora has been taken out with a wooden-legged man and a companion nobody wants to describe.

4. 4
   The Thames

   The chase downriver by police launch at full steam, past the Tower and the docks in the dusk - one of the best action sequences in the canon, and the reason the novel is still read.

5. 5
   Plumstead Marshes

   The Aurora run aground below Greenwich, Jonathan Small taken, and Tonga shot into the water - and the treasure gone over the side box by box across five miles of the Thames, which is Watson's good fortune.

6. 6
   Agra

   Small tells the story that started it: a fortress under siege in 1857, four men and a merchant's treasure, an oath and a murder - and thirty years and eight thousand miles later, a pearl arriving once a year in the post.