To get across the point that he is a lesser than those he speaks to.
Answer: The author will write, scribble, fidget, and meet an obstacle.
Explanation: Parallel structure occurs when similar elements, especially verbs, in a sentence are similar to one another. In the correct sentence, "The author will write, scribble, fidget, and meet an obstacle", the verbs, write, scribble, fidget, and meet are similar and are simple present tenses.
Go back to the text and re-read a passage where Watson made a discovery. If Sherlock praises him, you've got your answer. I'm sorry if this wasn't much help, but I don't have any text to go off of.