The ballet rehearsal painted in 1874 by French artist Edgar Degas looks, at first glance, like an innocent portrayal of dancers limbering up for a performance. But who’s that man in the shadowy background, straddling a chair, his top hat pulled down low over his eyes?

Models pose next to a 19th century bed of a French courtesan during a photo call for the upcoming exhibit Easy Virtue at the Van Gogh Museum in Amsterdam, Netherlands, Tuesday, Feb. 16, 2016. The exhibit, which runs from Feb. 19 till June 19 2016, shows prostitution through the eyes of Vincent van Gogh and many other well-known 19th-century artists, including Edgar Degas, Henri de Toulouse-Lautrec and Pablo Picasso. (AP Photo/Peter Dejong)

The ballet rehearsal painted in 1874 by French artist Edgar Degas looks, at first glance, like an innocent portrayal of dancers limbering up for a performance. But who’s that man in the shadowy background, straddling a chair, his top hat pulled down low over his eyes?

Models pose next to a 19th century bed of a French courtesan during a photo call for the upcoming exhibit Easy Virtue at the Van Gogh Museum in Amsterdam, Netherlands, Tuesday, Feb. 16, 2016. The exhibit, which runs from Feb. 19 till June 19 2016, shows prostitution through the eyes of Vincent van Gogh and many other well-known 19th-century artists, including Edgar Degas, Henri de Toulouse-Lautrec and Pablo Picasso. (AP Photo/Peter Dejong)