Pit of Darkness (1961)

Richard Logan, the partner in a safe making firm, is found unconscious on an old deserted bomb site. After regaining consciousness, he realizes that he has no recollection of the previous three weeks. Then he discovers that a private detective hired by his wife has been found murdered and a safe that his firm installed in a large country house has been cleverly opened and the contents are missing. So, with the help of his wife, he sets out to uncover the truth.

https://www.imdb.com/title/tt0055305/