What disturbs Lockwood and makes him get out of bed in Emily Brontë's Wuthering Heights?

Toward the beginning of Wuthering Heights, a raging snowstorm strands Mr. Lockwood at Heathcliff's estate, forcing him to spend the night. Already disturbed by the strange goings-on at Wuthering Heights, Mr. Lockwood sleeps fitfully and experiences a series of strange dreams. He gets up during his last, particularly creepy nightmare. In the nightmare, Lockwood hears a noise at the window, rousing him from his slumber to investigate the disturbance. To his horror, he encounters...

Toward the beginning of Wuthering Heights, a raging snowstorm strands Mr. Lockwood at Heathcliff's estate, forcing him to spend the night. Already disturbed by the strange goings-on at Wuthering Heights, Mr. Lockwood sleeps fitfully and experiences a series of strange dreams. He gets up during his last, particularly creepy nightmare. In the nightmare, Lockwood hears a noise at the window, rousing him from his slumber to investigate the disturbance. To his horror, he encounters the ghostly form of a girl begging to be let inside. The child says she is Catherine Linton, and Lockwood desperately tries to keep her out of his room. This occurrence is not only absolutely terrifying, but also serves as a brilliant example of foreshadowing. The ghostly apparition immediately puts us on our guard and encourages us to expect some truly dramatic history to be revealed, and we're not disappointed. Indeed, the ghostly child who disturbs Lockwood on a stormy night immediately sets the tone for the rest of the novel, as it tells the reader that the plot will be both dramatic and disturbing.