Answer:
Harold is suffering from jealous delusional disorder.
Step-by-step explanation:
Jealous delusional disorder is a subtype of delusional disorder in which the person suffering from it behaves abnormally due to the belief that their partner will be unfaithful to them. Even though the belief is unfounded, the person acts in a delusional, obsessive way, often being driven to extreme measures to prevent their partners from cheating. As we can see, Harold's behavior fits such definition. He has locked up his wife for the past ten years, being sure that he will be cheated on in case she ever leaves the house.