This book establishes new information about the likely content of ten lost plays from the period 1580-1642. These plays’ authors include Nashe, Heywood, and Dekker; and the plays themselves connect in direct ways to some of the most canonical dramas of English literature, including Hamlet, King Lear, The Changeling, and The Duchess of Malfi. The lost plays in question are: Terminus & Non Terminus (1586-8); Richard the Confessor (1593); Cutlack (1594); Bellendon (1594); Truth's Supplication to Candlelight (1600); Albere Galles (1602); Henry the Una (c. 1619); The Angel King (1624); The Duchess of Fernandina (c. 1630-42); and The Cardinal's Conspiracy (bef. 1639). From this list of bare titles, it is argued, can be reconstructed comedies, tragedies, and histories, whose leading characters included a saint, a robber, a Medici duchess, an impotent king, at least one pope, and an angel. In each case, newly-available digital research resources make it possible to interrogate the title and to identify the play's subject-matter, analogues, and likely genre. But these concrete examples raise wider theoretical problems: What is a lost play? What can, and cannot, be said about objects in this problematic category? Known lost plays from the early modern commercial theatre outnumber extant plays from that theatre: but how, in practice, can one investigate them? This book offers an innovative theoretical and practical frame for such work, putting digital humanities into action in the emerging field of lost play studies.