For around three centuries, the girl reading a letter in the dimly-lit solitude of a Johannes Vermeer painting gave no indication of what the message contained. Facing an open window, her figure gently curved as she scanned the note in her hands, her body appeared slight against the vacant wall behind her. But last week, the Gemäldegalerie Alte Meister in Dresden, Germany, where she’s been housed for most of her long life, has finally unveiled an amorous secret, hidden long ago beneath layers of paint. Ahead of its upcoming show about the celebrated Dutch painter, the museum has released an image of a drastically changed “Girl Reading a Letter at an Open Window,” which the Dutch artist painted between 1657 and 1659. Following a painstaking four-year-long restoration, the empty wall now shows a monumental painting of Cupid, discovered by X-ray in 1979, but now revealed for the first time. The unveiling of Cupid, the Roman god of love who is often represented as a winged boy, gives the girl’s letter new connotations of affection, longing and desire. The painting will go on view at the Gemäldegalerie from September 10 along with nine of Vermeer’s other major works and 50 paintings by his Dutch peers. When the hidden Cupid was first found over four decades ago, it was believed the Delft-born artist had himself painted over it. X-rays of other famous artworks have often revealed early drafts, and Vermeer was known to rework his compositions, believing that the harmony of his paintings reflected the harmony of God, according to Stephan Koja, art historian and director of the Gemäldegalerie Alte Meister. “It was common sense to think that Vermeer had overpainted this part of his composition because he had done this several times,” Koja said in a video interview. “He really was a perfectionist trying to get the most calibrated and most convincing composition.” But when conservators began cleaning the painting in 2017, they found evidence suggesting otherwise. Varnish on the stretch of empty wall behind the young girl was a different color, and the consistency of the paint was different too, Koja said. When researchers investigated samples in an archaeometry laboratory, they found dirt hiding in between layers of paint, signaling that someone else had added the overpaint much later. “We realized that the dirt meant that the painting was finished; it was exposed to the light and to the circumstances of a room for several decades,” Koja said. Now, the team involved believe it was painted over sometime in the early 18th century. But as to who did it, they can only guess. Not the only mystery The hidden Cupid is far from the only mystery of the Baroque artist’s life. The painter, like the enigmatic Renaissance master Leonardo da Vinci, had a preciously small output, with only around 34 canvases thought to have survived to today. He’s best known for his delicate interior scenes featuring solitary figures bathed in window light, hinting at narratives left intentionally vague. “(With) the single person lost in her thoughts, there’s a certain mystery, so we can relate to the feelings, emotions of the persons we see,” Koja said. “In a way, none of his contemporaries were able to do that.” The identities of Vermeer’s subjects are an enigma, too, including the woman in his most famous work, “Girl with a Pearl Earring.” Art historians are also still debating the techniques he used to create his optical illusions, particularly the question of whether he used a “camera obscura” – a dark room with a pinhole that projects a photographic image – to create his depth of field. It’s not even known where Vermeer learned to paint or who he learned from – a lineage that is typically well-documented for art history’s masters. Who painted over Cupid in “Girl Reading a Letter at the Open Window,” or why they did, may never be solved. The painting came from a French collection in the early 18th century, when Vermeer wasn’t well known – he had died in deep debt in 1675. Koja suggested that the painting may have been modified to more closely resemble the work of Rembrandt, possibly by the collection’s Flemish steward, who was also an artist. Altering someone else’s painting “was quite typical at the time,” Koja said. “Paintings have been changed according to taste… Nowadays, we think it’s completely inconceivable how you could touch a Vermeer but others (in) centuries before us were not that hesitant.” Several other Vermeer paintings were inexplicably altered, as well, Koja explained, from an entire blue sky painted into his early work “Diana and her Companions” to a modified picture frame in “Woman Holding a Balance.” (Both paintings have since been restored to their original compositions.) A familiar face To recover the Cupid, conservators at Dresden State Art Collections decided not to remove the original 17th-century varnish, but instead meticulously chipped away at layers of paint with a medical scalpel under a microscope with 120x magnification, according to Koja. The process took two and a half years, with only a few square millimeters covered each day. The Cupid they revealed was a familiar one. Standing upright, his left arm raised and his right arm holding a bow, the blond, chubby cherub has appeared in other Vermeer works. The god of love plays a supporting role in “Girl Interrupted at Her Music,” housed by the Frick Collection in New York, as well as in “Young Woman Standing at a Virginal,” which the Dresden museum has borrowed from the National Gallery in London for its new show. Koja said it is suspected that the newly discovered Cupid was based on a real painting in the artist’s possession. An inventory of his widow’s belongings from 1676 references “a Cupid,” according to The Art Newspaper. His appearance alters the meaning of one of Vermeer’s most pivotal works – one that represented a major shift in the artist’s career. Vermeer’s earliest paintings were not set in contemporary middle-class homes, but were grand works depicting religious and mythological subjects, from Jesus Christ to the goddess Diana. By the late 1650s, however, he had begun turning his eye to modern subjects – what became known as “genre paintings” of everyday life that are the hallmark of the Dutch Golden Age. “‘Girl Reading a Letter By the Window’ is really the essential piece of his transformation from a history painter to the painter of modern life – to the Vermeer we know today,” Koja said. Soon after completing the painting, the artist embarked on his most famous subjects and motifs: young women (and the occasional man) lost in thought in the quietude of rooms cast with mid-day light. The viewer’s presence can be sensed, too, as we peer in on figures playing music, reading mysterious letters or contemplating objects heavy with philosophical meaning. Vermeer’s subjects are sometimes interrupted by our presence, turning to gaze at our intrusion. “What’s so fantastic about Vermeer is that he leaves things open, and leaves them to our imagination,” Koja said. “And it’s (like) every kind of art – be it music, theater or film. I think you like most of the ones that have a certain mystery to them… like movie directors who give you clues and then let you finish the idea. This is something which Vermeer mastered.” Motion caption: The restoration of “Girl Reading a Letter at an Open Window.” Photographs courtesy of the Gemäldegalerie Alte Meister.