Violet, the Dowager Countess of Grantham (Maggie Smith) inherits a villa in the South of France from an old friend and decides to leave it to Sybil and Tom's daughter Sibbie, because she's the only one of her great-grandchildren whose future isn't secure. Meanwhile, a filmmaker (Hugh Dancy) gets permission from Mary (Michelle Dockery) to shoot a moving picture at Downton Abbey. Robert (Hugh Bonneville) thinks having actors and actresses hanging around plastered in makeup is a terrible idea, but other members of the family — and the servants — are thrilled.

In order to miss Mary's "frightful film," as Robert calls it, some of the family members, including Robert, Cora (Elizabeth McGovern), Edith (Laura Carmichael), Bertie (Harry Hadden-Paton), Rosamund (Samantha Bond), Tom (Allen Leech) and his new bride Lucy (Tuppence Middleton), as well as Lucy's mother Maud (Imelda Staunton), travel to the south of France to solve the mystery of why Violet's friend left her a villa.