I think Barn has become conscience stricken about RT Maggie and feels a certain amount of guilt about what he almost succeeded in doing to her. Anyway, that's the best explanation I can come up with.
His sadness increasing with every moment he watches the young marrieds, Barnabas finally pulls himself together and asks Maggie to excuse him. Maggie says, Elizabeth told me how wonderful you’ve been. With manly modesty he replies, Quentin’s recovery will be thanks enough. Quentin pulls himself up to add, Of course you’re welcome at Collinwood.
Maggie and Quentin throw themselves into each other's arms as Quentin's strength returns. He promises that nothing will hurt them again. Barn listens miserably outside the drawing room doors.
Meanwhile, in PT, Loomis House has electricity, so there's a phone somewhere, and Will and Carolyn know about Quentin's heart attack. Carolyn and Will are arguing. Carolyn refuses to be Barn's slave and threatens to expose him. Will pleads with her not to. If you want to stay a slave, you can go right ahead, she retorts. Barnabas only wants to get back to his own time, Will pleads. Then we can forget that this ever happened. He’ll never get back, Carolyn retorts, and I’m not going to wait another minute. I strongly suggest that you do, says Barnabas, who has suddenly materialized behind them. I have been here long enough to hear words I would have preferred not to have heard. His shadow falls across Carolyn, who screams as he comes within biting range.
Will begs Carolyn to tell Barn she didn't mean it, but she defiantly says that she does. When he expresses concern for Quentin, she taunts Barn that he isn't related to anyone at Collinwood. He replies calmly that he considers any Collins a relation, including PT Carolyn. You’re not a Collins, Carolyn says, even angrier than before. You’re not even human! Will angrily warns her to stop. She runs to his arms, declaring, We can’t live this way! Barnabas observes quietly, One does not always choose the circumstances under which he lives. No one knows that better than I. Go away and leave us alone, Carolyn says miserably. This is the one place than can give me a chance to get back to my own time, Barnabas replies. I must speak to Will alone. Carolyn looks at Barnabas and then at Will, who nods reassuringly. Barnabas warns Carolyn once more: If you expose me, it will mean your and Will’s destruction. As Carolyn turns to leave, Will grabs her hand and kisses it. You wouldn’t! Carolyn says as she leaves the room. I would without hesitation, Barnabas replies simply. Realizing he is telling the truth, she leaves.
Barn orders Will to open the cupboard under the stairs and orders him not to let him (B.) leave. While they listen as Maggie comes by and tells Carolyn the good news about Quentin, Will finally realizes why. Listening to Maggie sing Barn's praises has the predictable effect, and he orders Will to open the panel, but he brandishes the cross, forcing Barnabas to turn aside even as he orders Will to put it away. For reasons best known to herself, Carolyn opens the panel, unaware of Barnabas’s plight. Despite Carolyn’s screams, Barnabas seizes the opportunity to conk Will a few times with his cane, simply because he is available and even though he is not the real object of Barnabas’s anger. A few quick steps take him outside the house, without a thought for Will and Carolyn. As the dogs howl all around him, whatever remorse he may feel is quickly overwhelmed by desire as he starts determinedly for Collinwood.
Will lies on the sofa while Carolyn tends to his injuries. He tells Carolyn of the danger, and she agrees to warn Maggie.
Barnabas is just outside the front door at Collinwood, still trying to resist temptation. He slips into the shadows when he hears running footsteps, but when he sees it’s Carolyn, he warns her of the consequences of interfering. He is about to demonstrate, but from inside the house, Maggie has heard them talking and opens the door. With Barnabas concealed but listening, Carolyn lamely says she forgot to ask if there was anything she and Will could do to help. No, Maggie says, but thank you for asking. You might want to go to the hospital to stay with Quentin, Carolyn suggests with all the daring she can muster. Quentin insisted I come home, Maggie replies. Carolyn leaves, bitterly aware of her failure. After Maggie shuts the front door, the dogs howl again as Barnabas looks up at the bedroom windows in anticipation of conquest. For a moment, he turns sad, thinking, Will failed to stop me, and so I punished him, even though he was acting on my orders. Now Carolyn has failed too. But he is not deterred for long.
Sometime later (at 3:15), Maggie is sleeping peacefully in bed. (They can show her in a double bed, since she’s the only one in it.) Suddenly we see a bat hovering just outside the window; a moment later Barnabas has materialized in the room. He studies the sleeping Maggie for a moment; perhaps his innate decency puts up one last struggle. But the struggle is vain. Fangs bared, he leans over the bed to strike....