With respect to the author himself, there were several displays devoted to personal artifacts of Conan Doyle, including a handwritten note where he brags about his golf score, as well as photos and notes depicting his belief in spiritualism. His second wife was a medium and would hold seances to try to contact Doyle's oldest son who died of pneumonia towards the end of WWI. There were examples of "spirit writing" where spirits would convey messages to the living by guiding the hand that held the pen. One photo of Holmes and his wife shows a bright glowing light behind them, similar to what would appear if a camera flash reflected in a pane of glass. They believed this to be a spirit photo.
This was an insightful exhibit that encourages you to run out and borrow the tomes of Sherlock Holmes from your nearest public library.