Poll and Theo are the two younger siblings of four, they live in a nice house in London at the turn of the 20th Century. Father owns up to something he didn't do which has grave repercussions, and it means that the family are left without money and without Father too - as he has gone off to join his brother in California. The children and Mother are now forced to decamp to Norfolk, to live next door to two elderly spinster aunts in a very small terraced house.
In the course of a year, Poll and Theo learn quite a lot about how grownups behave; how everything is not necessarily what it seems; they grow up (literally in Theo's case) and begin to understand the world according to adults.
It's a lovely old fashioned adventure, great for good readers eight and upwards. I did wonder what a young reader might make of the statement "......the sound of Mother's stays creaking". For those of you who are bewildered, stays were a kind of corset - today's equivalent might be Spanks!