Deception is a central theme in "The Open Window," where the young character Vera uses her imagination to weave intricate tales that manipulate those around her. Her skillful storytelling not only entertains her but also reveals the gullibility of her audience. Through Vera's actions, the story explores how easily people can be deceived when they accept information without question.

Vera's motivations for lying are rooted in her desire for amusement and control. She enjoys creating believable narratives that unsettle others, finding entertainment in their reactions. Her ability to concoct elaborate stories is a testament to her intelligence and imagination. This is evident when she tells Framton Nuttel a fabricated story about her aunt's husband and brothers, leading him to believe they are ghosts when they return from hunting. Her deception is further highlighted by her calm demeanor and quick thinking, as she invents another story to explain Nuttel's hasty departure.

"I expect it was the spaniel," said the niece calmly; "he told me he had a horror of dogs. He was once hunted into a cemetery somewhere on the banks of the Ganges by a pack of pariah dogs, and had to spend the night in a newly dug grave with the creatures snarling and grinning and foaming just above him. Enough to make anyone lose their nerve."

The story also reveals a broader truth about human nature: people are prone to believe what they are told without seeking verification. This gullibility is exploited by Vera, who uses her storytelling prowess to manipulate both Framton Nuttel and her own family. Her tales are accepted without question, illustrating how easily deception can occur when critical thinking is absent.

Vera's character is crafted to fit the needs of the plot, serving as a catalyst for the story's events. Her mischievous nature and imaginative mind are products of her environment, where she is confined to a country house and forced to play hostess. Her boredom and resentment towards her situation drive her to create chaos through her stories. This is evident when she convinces Nuttel of the ghostly return of the hunters, and later, when she fabricates a tale about his fear of dogs.

"Here they are at last!" she cried. "Just in time for tea, and don't they look as if they were muddy up to the eyes!"

Framton shivered slightly and turned towards the niece with a look intended to convey sympathetic comprehension. The child was staring out through the open window with a dazed horror in her eyes. 

Ultimately, Vera's habitual storytelling is confirmed by the story's closing line, "Romance at short notice was her speciality." This highlights her talent for improvisation and her enjoyment in crafting deceptive tales. Through Vera's actions, "The Open Window" explores the theme of deception, showcasing the ease with which a skilled storyteller can manipulate those who are willing to believe without question.