Assassination vehicles in Elizabethan and Jacobean tragedies sometimes involve meta-theatrical court festival massacres: court performances embedded within full-length drama, resulting in violent death or trauma to characters in the play. During his career as a playwright (c. 1600-08), John Marston pioneered the masquerade-within as a popular subcategory of court festival massacre. Were such underhand festival appropriations wholly inspired by stage precedents? Or did they also occur in real life? Whether its deaths were accidental or resulted from a botched assassination plot, the 1393 Bal des Ardents was hugely culturally and politically influential. My researches identify the conspiracy rumours encouraged in the wake of the 1393 Paris disaster and two English conspiracies of 1397 and 1400 linked to court festivals, as key to a fresh approach to the meta-theatrical court festival massacre, and to interpretation of two plays traditionally discussed together, which refer to these English conspiracies, Shakespeare’s Richard II and the anonymous Thomas of Woodstock. My analysis supports a post-Elizabethan dating of Woodstock, and encourages the hypothesis that it could be the so-called Scots’ Mine Play of 1608, the lost Jacobean play thought by some to have ended Marston’s career as a playwright.