Sir Arthur Conan Doyle never actually wrote that line in any of his books. But I think he might have approved of puzzle caches. From its use in the short story "The Adventure of the Dancing Men" we know that he had a least a passing familiarity with cryptography. In the story, Sherlock Holmes uses frequency analysis to decode a series of messages similar to the image below that have been encoded with a simple substitution cipher. Unfortunately, that method will not help you here.
If you've read everything up to this point (and I don't mean the dancing men image; that's just decorative), you have enough information to be able to discover the meaning of the following list of numbers.
39, 76, 92, 98, 95, 41, 50, 90, 18, 75, 81, 70, 8, 92, 37, 74, 33, 57, 19, 76, 102, 18, 4, 99, 37, 66, 99, 63, 41, 79, 23, 63, 10, 92, 99, 89, 43, 11, 76, 44, 81, 80, 26, 49, 9, 52, 39, 76, 41, 63, 66, 63, 64, 44, 63, 63, 14, 73, 74, 99, 10, 43, 70, 63, 77, 32, 80, 81, 91, 76, 77, 11, 65, 60, 53, 10, 63, 73, 72, 88, 68, 68, 68, 77, 32, 80, 22, 33, 60, 66, 74, 99, 14, 52, 8, 41, 63, 1, 92, 28, 66, 44, 68, 66, 85, 60, 66, 65, 1, 53, 88, 73, 63, 68, 7, 66, 99, 32, 88, 99, 63, 38, 40, 99, 88, 8, 102, 53, 60, 99, 84, 76, 53, 11, 52, 22, 67, 45, 99, 63, 14, 53, 54, 76, 41, 63, 39, 8, 92, 47, 45, 63, 57, 76, 76, 19, 53, 102, 31, 100, 8, 37, 18, 58, 47, 12, 8, 92, 87, 57, 33, 31, 68, 66, 76, 11, 63, 57, 49, 43, 44, 68, 3, 76, 98, 36, 95, 102, 66, 57, 76, 27, 19, 96, 76, 11, 81, 13, 77, 10, 63, 75, 49, 73, 53, 62, 57, 8, 29, 47, 52, 63, 66, 47, 65, 10, 8, 88, 69, 80, 26, 53, 87, 22, 70, 8, 28, 68, 66, 63, 32, 37, 99, 99, 38, 43, 74, 63, 11, 90, 70, 102, 77, 41, 99, 59, 76, 77, 60, 52, 30, 99, 45, 8, 22, 74, 76, 63, 77, 64, 1, 81, 42, 77, 102, 92, 81, 68, 62, 47, 102, 66, 74, 99, 50, 69, 8, 93, 63, 67, 92, 60, 66, 44, 63, 66, 18, 7, 66, 65, 80, 77, 88, 81, 63, 68, 28, 66, 68, 32, 88, 99, 63, 38, 30, 63, 37, 8, 41, 77, 102, 99, 15, 8, 53, 28, 52, 40, 99, 37, 8, 30, 68, 88, 76, 16, 53, 54, 42, 77, 28, 92, 69, 68, 51, 31, 8, 31, 63, 81, 90, 72, 89, 65, 98, 47, 6, 67, 68