Holmes and Watson go to Dartmoor because
- they think horse thieves have taken Silver Blaze there
- Silver Blaze disappeared from a stable there
- Silver Blaze is going to run in a race there
There was a lot of security at the stable because
- there are many thieves on Dartmoor
- Colonel Ross is very security-conscious
- the horse was soon to run in a major race
Fitzroy Simpson wanted
- information about horses
- to steal Silver Blaze
- to kill John Straker
Hunter, the stable boy, didn't stop Silve Blaze leaving his stable because
- he had eaten opium
- he took a bribe
- the horse ran out too quickly
Holmes decides Silver Blaze is at Mapleton Stables after he
- deduces this is the only possible place the horse could be
- follows the horse's tracks across the moor
- persuades Silas Brown to admit he is hiding the horse
Holmes becomes suspicious of Straker, the dead trainer, because
- his footprints were on the moor
- he was the only person who could have drugged Hunter
- trainers often bet against their own horses
He discovers Straker's motive for the crime when he
- speaks to his wife
- finds a bill in his pocket
- finds a scalpel among his belongings
Straker needed extra money
- to buy dresses for his wife
- to support a secret lover
- to pay for his gambling habit
On the night he died, he took the scalpel to the stables
- to defend himself against someone trying to break in
- to kill the horse so it couldn't run in the race
- to injure the horse so it would lose the race
Holmes' theory is confirmed by the behaviour of
- the cows and the cat
- the pigs and the chickens
- the sheep and the dog