Officers say they received a call from a neighbour and discovered the woman and a boy, about eight years old, in medical distress.
They were soon pronounced dead at the scene.
Police say a man, other children and some extended family members who may have also lived in the home have been found and are safe.
A suspicious vehicle was spotted leaving and Mounties later pulled it over on a highway about 80 kilometres north near Didsbury.
Police are talking with the driver, but don't know yet if the person is related to the case.