How did Nicholas get the better of his aunt when the other children set off on the expedition?
According to Saki's story, we have two instances where Nicholas gets the better of his aunt, after the children leave for Jagborough Beach:
1)He manages to secure passage into the coveted lumber room by tricking his aunt. After the children leave, Nicholas manages to feign a few attempts to get into the gooseberry garden (which he has been forbidden to enter); in doing so, he diverts his aunt's attention to the double doors which open into the gooseberry orchard.
While his aunt watches the doors steadily (Nicholas tells us that she is a 'woman of few ideas'), Nicholas manages to retrieve the key to the lumber room. There, he enjoys poring over a rich tapestry depicting a hunting scene. His imagination runs wild as he tries to imagine the fate of the hunting party in the event of a wolf ambush. Nicholas thoroughly enjoys himself in handling previously forbidden objects such as brass figurines, a china duck teapot, ornamental candlesticks, and a book depicting various types of exotic birds.
2)When his aunt becomes trapped in the rain-water tank, Nicholas manages to toy with her and to exasperate her mercilessly. When she impatiently demands the boy bring over a ladder, Nicholas demures. He tells her that he doesn't think her voice belongs to his aunt. He also tells her that he is forbidden to enter the gooseberry garden and so, cannot help her out of her predicament.
With ruthless cunning in the guise of a conscientious spirit, Nicholas boldly proceeds to test his aunt. He plays the part of innocence by asking her about the possibility of having strawberry jam for tea if he helps her. By now, his aunt is furious; she promises him the jam, but spitefully decides that she will deny him the treat once she gets out. However, Nicholas gets the last laugh when he proclaims that only the Devil would tempt him with strawberry jam: he cunningly asserts that since only he and the Devil know of the four jars in the store-cupboard, the person in the tank must be the Devil himself.
With this last repartee, Nicholas leaves his aunt to suffer thirty-five long minutes in the rain-water tank before she is rescued by a kitchen-maid.