Dominique is Dead Full Horror Movie - psychological and supernatural

This is a 1979 British psychological horror film directed by Michael Anderson, featuring Cliff Robertson and Jean Simmons.
The story centers on David Ballard (Robertson), a wealthy businessman who manipulates his wife, Dominique (Simmons), into believing she is losing her sanity. Overwhelmed by his psychological torment, Dominique ultimately takes her own life by hanging herself in their home's conservatory. Following her death, David experiences unsettling occurrences, including visions of Dominique and the sound of a piano playing mysteriously at night. These events lead him to question whether he is being haunted by her spirit or succumbing to his own guilt-induced delusions.
The film delves into themes of psychological manipulation, guilt, and the supernatural, creating a suspenseful narrative that keeps you questioning the nature of reality and the afterlife.