Lockwood is a tenant of Heathcliff's, renting Thrushcross Grange. As a conventional and outgoing person, he acts as a foil to the strange, fierce landlord he has unwittingly fallen in with. Lockwood tells us that, prior to arriving there, he had been at the seashore where he met a "real goddess" but froze up after she showed a response to his advances: "I ... shrunk icily into myself, like a snail." He was thus perceived as leading her on and gained a reputation for "deliberate heartlessness."
Lockwood tries to be friendly to Heathcliff, at first assessing him a "capital" fellow. However, when Heathcliff's dogs pin him to the ground as Heathcliff laughs at him, Lockwood begins to get more and more agitated. When he is trapped at Wuthering Heights for the night, he finds an old diary in the room in which he sleeps, and he sees the names Catherine Earnshaw and Catherine Heathcliff carved into the windowsill. He reads Catherine's few diary entries and that night dreams Catherine is trying to get in through the window. He also witnesses Heathcliff crying out to her.
When Lockwood gets sick at Thrushcross Grange, he persuades the servant Nelly to tell him the story of Catherine and Heathcliff, about whom he has become curious. An intense and unusual tale unfolds for him--and for us.
Lockwood is renting Thrushcross Grange, which Heathcliff owns. Thus, their relationship is one of a landlord and his tenant. At the beginning of the novel, Lockwood has not met Heathcliff and decides to visit him at Wuthering Heights. It is this encounter which provides the basis for the rest of the story. Lockwood is treated so badly and experiences such unnatural events that he becomes curious about Heathcliff and the other people who inhabit Wuthering Heights. Lockwood returns to Thrushcross Grange and asks his servant, Nelly, to tell him the story. Nelly then reveals the strange history of both Wuthering Heights and Thrushcross Grange.
Lockwood is no more than a tenant to Heathcliff renting Thrushcross Grange for the summer time. In the first chapter of Wuthering Heights Lockwood talks about going and making the owner, Heathcliff, his acquaintance since he will be staying there.
‘Mr. Lockwood, your new tenant, sir. I do myself the honour of calling as soon as possible after my arrival, to express the hope that I have not inconvenienced you by my perseverance in soliciting the occupation of Thrushcross Grange: I heard yesterday you had had some thoughts—’ Chapter 1
The only reason Lockwood begins to learn things about Heathcliff is because he complained to Nelly and Nelly tells him about how Heathcliff became what he is today.