I just finished a replay of Haunted Past: Realm of Ghosts CE, a game I bought back in 2011. The Bonus game ended with you going back in time and space to Castle Kildare in 1912 to fix things, so it seems to have been a teaser for an upcoming game. Was there ever another Haunted Past game after this?

I've played Haunted Past: Realm of Ghosts, and I don't recall there ever being a sequel.

Too bad.
I couldn't find anything about another "Haunted Past" game either.

I believe the developer, Gogii Games, stopped making games for PC and went exclusively to mobile, unfortunately. They had a number of interesting games released on Big Fish in the past.