Watch National Theatre Live: The Authenticator (2026) : Full Movie Online Free Soon after inheriting her family's stately home, eccentric artist Fenella Harford discovers a stash of hidden diaries and enlists a young academic, Marva, to confirm their authenticity. Joined by Marva’s brilliant but overlooked mentor, Abi, the three women come together to seek the truth, soon realising that secrets at the heart of Harford Hall were darker than they could have imagined. A gripping gothic psychological thriller, The Authenticator reunites writer Winsome Pinnock with director Miranda Cromwell, following their acclaimed production, "Rockets and Blue Lights". Stage play performed at the Dorfman Theatre, National Theatre, in London, UK.