As supper is cleared from the table, and their parents relax into the evening, the young Sybil Thorndike and her brother Russell are staging a play. The makeshift theatre they have erected in a spare room of their house in Gainsborough gives Sybil her first taste of the stage, with a gathered audience of household servants, happy to indulge the passions of the two precocious children. It is a play of Sybil’s own devising, a bloody little shocker called The Dentist’s Cure, or, Saw Their Silly Heads Off, consciously or unconsciously cribbed from overheard fragments of Victorian penny dreadful The String of Pearls, with a cruel tooth-puller in place of macabre Sweeney Todd. Quietly, the maids pray that there will be less murder in this one than in weeks previous, the bloodstains from earlier performances of the similarly improvised The Blood on the Bedpost, The Murder of the White Mice and The Nun’s Revenge having caused some consternation with the mistress of the house. So it was that the future Dame Sybil Thorndike, who would become perhaps the most respected and revered British actress of her age, together with her similarly vaunted brother, displayed her early but enduring enthusiasm for horror on the stage. In 1921 she was quoted as declaring ‘Horrors have been my meat and drink day and night since I was a tiny child’, her comment published in the Grand Guignol Annual Review, the record created by the London theatre in which she starred, where her work and dedication played a major role in its success. This article will examine Sybil’s involvement with London’s Grand Guignol, José Levy’s bold transplantation of the Parisian form to London’s Little Theatre, considering her motives for joining the company, her work within it, the work of her husband, noted director Sir Lewis Casson, and her brother who completed what was a truly family affair, as well as the significance of her participation in the wider cultural history of the Grand Guignol.