To discover an ‘unknown’ is the dream of anyone connected with the arts and in Johannes Thopas (c.1626-1688/95) we have just that. This book catalogues the exhibition now transfering from Aachen to the Rembrandt House Museum, Amsterdam (12 July–5 October). The curator is Rudi Ekkart, who discovered Thopas’s meticulous lead-pencil (plumbago) drawings on parchment as an art-history student in the early 1970s, when he had unlimited access to the University of Leiden’s famous drawing collection.