Rick mentions 3 tour groups to experience the underground of Edinburgh (all with a bit of spookiness). The Real Mary King's Close, Auld Reekie Tours and Cadies and Witchery Tours. Will only have time for one of these. Any recommendations?
I don't remember who we used about five years ago, but do it! It's a great experience!
In June we used Mercat Tours for a guided tour of the Royal Mile and Edinburgh Castle. Our guide was excellent! They offer underground/spooky tours as well.
Here's a couple of reviews/comments I found on the forum.
https://community.ricksteves.com/travel-forum/scotland/closes-in-edinburgh
https://community.ricksteves.com/travel-forum/scotland/walking-tours-in-edinbourgh
https://community.ricksteves.com/travel-forum/trip-reports/trip-report-scotland-in-9-days-or-we-ve-never-met-a-sticky-toffee-pudding-we-didn-t-like
https://community.ricksteves.com/travel-forum/scotland/tips-for-traveling-with-a-tween-in-scotland
We enjoyed the Real Mary Close.
I did two tours, one into Mary King’s Close, and the other was a ghosts and torture tour. I can’t recall the name of the tour operator, but I liked the ghost and torture tour much better. It was a more interesting experience, whereas the Mary King one was mostly a history lesson. I do like history, but the ghost tour was fun, and spooky.
We did Mary King back in May: it was interesting but not spooky at all. More like plague/sanitation focused.
We did an Auld Reekie tour last month, and it exceeded our expectations. It was the daytime one, appropriate for our kids (7, 11), and we all loved it. Can't speak to the other groups, but I had looked through lots of reviews and had determined it was the best one for us.
All the best.