Father Brown - Season 3 Episode 2

Father Brown and Lady Felicia are visiting a museum owned by her Egyptologist friend Sir Raleigh Beresford, who has just married the much younger Caterina. Caterina insists on opening a sarcophagus, an action which allegedly carries a curse and some time later she is found dying in a locked room. Sir Ralph's son Leo was having an affair with Caterina, making him a prime suspect, but then Raleigh's adoring secretary Valerie admits to the murder. Father Brown does not believe her and discredits her account before unmasking the real killer.