Alfred Hitchcock Presents S05E22 - Across the Threshold

Sofie Winter is a wealthy widow that tries to control the life of her son Hubert. She misses her husband dearly and often thinks of him as waiting just across the threshold for her. She wants to talk to her husband wondering whether he is lonely and wants her to come to him. Hubert convinces his mother that he knows a medium. The "medium" is actually his girlfriend Irma. Irma tells Sofie that her dead husband is lonely and that he wants her to join them. Sofie agrees to take a fatal dose of medicine, but stalls. Hubert grows upset and gets himself a drink. He soon dies. His mother poisoned the drink. She wanted her son to join his parents in the afterlife.