The article is devoted to the design drawing for the monumental rococo high altar, recently discovered in the collection of the National Museum in Warsaw. A profound analysis of the drawing leads to a series of conclusions. Firstly, its formal features: composition, forms, drawing technique (the brushstroke marks, the wash) indicate beyond any doubt that the drawing was made by Johann Georg Plersch (approx. 1700–1774) – a Warsaw-based sculptor at the courts of August II and August III, and one of the most prominent Warsavian artists of the epoch. Secondly, the drawing is the design for the high altar in the Dominican Church in Lublin, as evidenced by its proportions, the pieces of the existing architecture and the extremely distinctive iconography of symbolic and figural representations. The altar was devoted to the glorification of the Cross of Christ, whose glorious image is carried by angels and which is also paid homage to by the grand figures of Constantine the Great and Saint Helena, and above all else, the relics of the Holy Cross, stored in the peculiarly shaped 17th century reliquary (well known to researchers of the Lublin temple) placed in the open arcade within the main body of the church. They are the main point of reference for the whole design, both in terms of ideology and composition. The subject matter of the paper is the drawing itself, with its interesting Warsavian, Roman and Parisian archetypes. The shrouded history of the commission placed for the construction of the stone altar, initially given to Cracovian masters (more precisely, to Francesco Placidi) and then assigned to Warsaw-based artists adds to the mystery, with the work never being installed in the intended location, i.e., in the presbytery of the Lublin church, at the exit of the Chapel of the Holy Cross (also known as the Tyszkiewicz chapel). Its stone elements were crafted and rafted along the Vistula River to Puławy, where it disappeared without a trace.