Frankenstein and the Monster from Hell (1974) on Netflix

A body snatchers caught by a police sergeant and he snitches the name and address of his client, Dr. Simon Helder. The doctor is arrested and accused of sorcery, and sent to a psychiatric institution. There he meets Dr. Carl Victor, a.k.a. Baron Victor Frankenstein, who is presumed dead but actually he is alive and secretly continuing his experiments reanimating the dead. Dr. Helder worships Frankenstein and has studied his works and he becomes his assistant together with the dumb Sarah. One day, Dr. Helder discovers Dr. Frankenstein's secret laboratory and accidentally releases a Monster in the institution, bringing panic to the inmates and staff.