What conclusions can be drawn from Heathcliff's behavior after Lockwood leaves the bedroom in Chapter 3 of Wuthering Heights?

Chapter three is pivotal chapter in the book. This is the chapter where Lockwood tries to spend the night in the crazy old fashioned bed that had been Catherine’s, sees her carvings in the window sill, reads from her journal, and has the horrible dream about the sermon and Catherine at the window trying to get in. Even though Lockwood has only dreamed about Catherine’s ghost “walking the earth these twenty years,” in practical terms Catherine’s spirit has haunted him – her spirit clearly dominates the room. This is no doubt the reason, as Zillah says when she leads Lockwood to the room at the start of the chapter, that Heathcliff had “an odd notion” about the room. But then, she says, there had been “so many queer goings on” she couldn’t begin to explain.

Zillah’s resignation suggests that she is an unwilling spectator to Heathcliff’s psychological battle with Catherine, in the same way that Lockwood becomes an unwilling (and unwitting) participant. Heathcliff’s reaction to Lockwood’s calling out can only be classed as another of these “queer” events. Heathcliff enters the room, but clearly (and uncharacteristically) is in awe or afraid of what he might find: he calls out in a “half whisper” to see if anyone is there. He hopes to find Catherine’s ghost, returned to him; imagine his fury to find it is only Lockwood! It is as if a stranger had blundered into his most secret thoughts (another “penetralium,” to use the word from Chapter one). When Lockwood tries to explain, Heathcliff bursts out: “'What can you mean by talking in this way to me!’ thundered Heathcliff with savage vehemence. ‘How—how dare you, under my roof?—God! he’s mad to speak so!’” But when Lockwood finishes explaining his dream, and leaves the room, he hears Heathcliff’s grief:

“He got on to the bed, and wrenched open the lattice, bursting, as he pulled at it, into an uncontrollable passion of tears. ‘Come in! come in!’ he sobbed. ‘Cathy, do come. Oh, do—once more! Oh! my heart’s darling! hear me this time, Catherine, at last!”

Lockwood is embarrassed to hear this outburst: “There was such anguish in the gush of grief that accompanied this raving, that my compassion made me overlook its folly, and I drew off, half angry to have listened at all.” His embarrassment is like ours as readers. Heathcliff on the surface seems psychotic and anti-social -- a man bent on revenge at any cost. Up to this point in the book we have understood him to be, for whatever reason, the antithesis of the country gentleman Lockwood hopes to find for a neighbor. When we, as readers, overhear with Lockwood Heathcliff’s private grief, we get a glimpse of the titanic forces that are at work within him. He’s very different, and in some ways more frightening, than we ever expected.