This is "An Officer dictating a Letter" painted in the Dutch north by Gerard ter Borch. The central figure, dressed in military attire, gestures as he dictates to the man with the quill. Meanwhile, their comrade in the impressive blue jerkin stares directly out of the painting, catching our eye with his faintly amused expression. He's a messenger, waiting for the letter to be finished.
Take a closer look at the floor just in front of the dog's hind leg. What looks like a patch on the canvas is actually the faded outline of a playing card – the ace of hearts. Originally, ter Borch had painted this in more detail, but later changed his mind, making the situation even more mysterious. The presence of this card would have suggested that the letter wasn't a vital military message, but rather a love letter.
The spaniel at our feet meets our eye as well, its expression bored rather than bemused – possibly because the writing has gone on for so long that one broken clay pipe has already been discarded on the floor. The artist seems to be creating an air of quiet reflection and enigma in this work, which is quite different from his earlier guardroom scenes.
An Officer dictating a Letter hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.