Very happy to see this well-written, unusual episode. I hope this signals an upturn in the quality of the series. As usual, the crime-detective parts were weak, but fortunately they were a small part of the episode.
What I liked are the strong sentimental aspects that, at the same time, were not heavy handed, showed gradual development and left some things unsaid/unexplained. They brought many aspects of the show together, were well integrated and actually quite realistic! Nice the way: father and son didn't reproach each-other and themselves severely much; showed how dad contributed to son's career with Sherlock Holmes stories; uncovered and solved mystery together; distributing cheap toys to disappointed kids was funny; learned more history of Adrian's background; bicycle references; and father's tolerance of son's fussiness