Harriet is arty and incompetent with a childlike daughter of nineteen but fortunately they have practical Sidonie to look after them - very fortunately since, unknown to Harriet, their dilapidated house is the hiding place for a heap of stolen jewellery which small-time crooks Sam and Bert have come to find. Impoverished, Harriet is persuaded to sell Sam the house so that she, Monica and Sidonie can move to the seaside on a profit. But, in this lighthearted comedy, the ever-practical Sidonie makes sure of even greater profits by smuggling out the treasure where 'no-one would ever think of looking for it'.