Restoration of Johannes Vermeer’s painting Girl Reading a Letter at an Open Window, painted around 1658, has revealed a long-hidden surprise – the figure of a Cupid on the wall behind the subject. It has long been known from X-ray studies that the Cupid had been painted over, but it was believed that this had been done by Vermeer himself; detailed chemical examination now suggests that the overpainting was done after Vermeer’s death, so the...