The Alfred Hitchcock Hour - Season 2 Episode 32 : Body in the Barn 1965

Bessie Carnby and her daughter Camilla have been feuding with their neighbors Henry and Samantha Wilkins. In order to patch things up Bessie invites them over for dinner. Samantha refuses to go, but Henry goes and tries to act friendly. Later, he disappears and Bessie sees Samantha digging a hole in her barn. Bessie accuses Samantha of murder and calls the police. The police dig up the hole and find a badly decomposing body. Samantha is executed for the crime, but later Henry returns claiming he went out to sea. He has inherited his wife's money and marries Camilla. Bessie realizes she has been tricked and, feeling guilty over having sent an innocent Samantha to her death, decides to bring Henry to justice by poisoning herself and making it look like he is responsible.