This is "A Cottage by a River with a Distant View of a Castle" painted in the Flemish style around 1650. David Teniers the Younger was known for his invented landscapes, and this view may show a castle in the distance that has yet to be identified.
Judging by the new shoots on the trees between the cottage and the river, this is a spring scene. The maid working hard in her cheerful red dress brightens the scene as she turns to look at the old man, who glances back at her - seemingly just a passing greeting. But then we see the shadowy figure in the doorway of the cottage.
An older woman leans back to look at the maid, her expression inscrutable, leaving us to interpret the story Teniers painted. This kind of interaction between interesting and comical characters is typical of Teniers' work. He often used these figures and settings in multiple paintings, such as "A View of a Village with Three Peasants talking in the Foreground".
The cottages in this painting show a thatcher's trademark - a crown made of reeds on the rooftop. A hoist is shown from both top windows, ready to haul the autumn harvest into the attic for storing.
Teniers was highly successful internationally and worked for prominent figures such as King Philip IV of Spain and Archduke Leopold William, the Governor of the Netherlands.
A Cottage by a River with a Distant View of a Castle 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.