This novella by Collins was first published in 1874 in the collection "The Frozen Deep and other stories" under the title "John Jago's Ghost; or The Dead Alive". Based on a real early 19th-century case, it is set in the US, and the solution to the mysterious disappearance/murder of John Jago is fairly easily discerned from the title. The narrator-protagonist is a youngish lawyer, on a foreign trip to cure his nervous complaint (well, so much for that), and he encounters no supernatural occurrences or Gothic contrivances, other than a couple of moonlit gardens. Instead, there is a steady buildup of characterization for four or five main players, including the aforementioned John Jago, as well as one of Collins' trademark Young Women Who Know Their Own Mind (this one demonstrates it in American idioms, though not too annoyingly).
There's a disappearance, the arrest of two overwhelmingly obvious suspects, several stages of trial (interestingly, we're taken through the whole rarely-described sequence of magistrate - Grand Jury - formal trial), a couple of confessions with coercion in question, a verdict, a newspaper advertisement and a coincidental discovery, all overlaid with a rather unnecessary romantic sub-plot that leaves us a little unsure whether the young lady in question really knows her own mind or not, so quickly does she change the object of her affections. But then, it's not a full-length novel.
A quick and easy read, and it has been republished (2005) as an interesting early fictionalization of a wrongful conviction in the US, along with a lot of contextual legal information on the same - that is not the edition I read.
If you read Collins because he tells a good story, this item will suit you fine; if you read him for his Gothic/supernatural/sensational aspects, don't be fooled by the title - there's next to nothing in that vein.