The look Stiles gives her over his shoulder when Deaton says she has to stand with him is like a punch in the gut.
He just seems so apologetic about the situation, like he wishes she wasn't being put in this position. It's like his eyes are saying, no sarcasm to be found, sorry my unadulterated love for you is forcing you into this. I know you don't feel the same, but right now there's no one else who can help me kill myself to save my dad. And I need to do that, 'cause I can't be alone, Lyds, I can't. So, please, just do this for me, just this once. I won't ask for anything ever again, and don't feel guilty if something goes wrong.
And in her head, she's responding, don't you dare, Stilinski, because she'll be damned if he doesn't know that he doesn't have to ask and he doesn't have to apologize, that she would never in a million years let him be lonely, and that it would absolutely destroy her if he left her alone in this mess, even more so if it was her fault. (And it's running like a mantra in the back of her head - You see that's the problem. You don't care about getting hurt. But you know how I'll feel? I'll be devastated. And if you die, I will literally go out of my freaking mind. You see, death doesn't happen to you, Lydia, it happens to everyone around you, okay? To all the people left standing at your funeral, trying to figure out how they're gonna live the rest of their lives now without you in it – and she wants to scream it back at him because now, this day, she knows she would too.)
But she can't for the life of her get any of these thoughts to come out of her mouth. She's closed up and internally berating herself because when she breaks away from his gaze, searching for a way to tell him, she realizes too late that it's like a confirmation of everything he's thinking. But she can't force herself to do anything more than stare at the spot on the floor somewhere to the left of his feet. As much as she knows he means to her, it's not as if it's easy being officially informed that she has some profound bound with a boy she's been denying for eight years. Not that it doesn't make sense.
That's the part that has her standing like a statue, unable to reassure him that it's okay, more than okay. The thing is, it makes perfect sense that she's his "tether." She knows how much he loves her. What scares her is that she doesn't think this is a one-way thing. If she is his (and the possession in those words fills her with a terror that sends a shiver down her spine and at the same time has a certain degree of appeal that makes heat start to creep up her neck), then logically he should be hers. And suddenly she can't avoid how important he really is to her, so much so that she wonders how long she's been carefully dogging the fact. Before she can stop herself, her thoughts go back to when she was with him on the locker room floor, grabbing his face and smashing her lips to his. Even now, she hasn't come up with a proper explanation of why she had done it. Sure she had known he needed to be distracted, and yeah, it had worked. But the answer she'd given him, the cause-and-effect logical version of it, was not how it had played out in her head at the time. At the time, all that was in her head was an unending string of StilesStilesStiles and then she was kissing him, no forethought at all. And it's driving her crazy now because she remembers ever millisecond of it - clutching his face, desperately trying to get him to relax, failing, crashing into him, and after a moment, feeling him sink into it. She remembers slowly breaking away and not being able to open her eyes because it was good, it was so good, so much better than she could have expected, and this ache grew in her chest the further away from him she moved and her hands were still out as if they wanted to grab on to him again and she had had to force herself to drop them and open her eyes and he was staring at her, breathing normally but just looking so lost and maybe she should just try again just to be sure it had worked -
She pulls herself back to vet's room. It's just in time to notice the hurt look on Scott's face as he looks between Allison and Isaac. She's distracted for a moment as she sympathizes with Scott because he hasn't been around enough to notice the bond forming between the love of his life and his closest supernatural friend. And then she empathizes with Allison because apparently tonight she's not the only one being officially informed of the depth of her feelings for a friend.
She automatically glances at Stiles to share a look, only to find that is back is to her. With everyone's attention on the love triangle, no one has seemed to notice that Stiles is hunched over a tub, clutching the sides with white knuckles. His head is hanging low so all Lydia can really see is his back. The view of it is made clearer because the angle of his arms and tight grip on the tub has made his shirt pulled taunt over it. His whole back is quivering slightly, so much tension there that it seems like he could physically shatter at any moment.
Before she can give it any thought, she's standing behind him, carefully placing a hand between his shoulder blades.
Almost immediately, the tension drains out of him, and he sags slightly, only really holding himself up by his clutch on the tub. His knuckles are still white though, so she starts to slowly rub up and down until his hands relax their grip. They stay that way for a short while until suddenly he's whipped around and looming over her, clutching her shoulders and staring at her, his face filled with so much anger and sorrow and feeling that she thinks she may combust.
She swallows her gasp but can't stop the shudder that runs through her as she stares up into his whiskey-colored eyes. His eyes grow wide, realizing he's scared her and he opens his mouth ready to apologize, but she stops him by grabbing one of his hands. His other hand drops from her shoulder and he looks at her, confused and for some reason slightly guarded (and that's wrong, it's so wrong, because if there is one person that she knows that's open and unfiltered it's Stiles and this guarded expression is just so un-Stiles-like that she needs to fix it now because if Stiles closes up from her she's certain she'll go mad). He glances down at their hands and then back up at her questioningly, expression still guarded.
She thinks quickly, trying to think of something that she can do that will tell him what she's been thinking. Finally, she lifts his hand slowly to her lips, squeezing her eyes shut and kissing his middle knuckle.
After a moment she pulls away, looking back up at him. His eyes are slightly wide but they soften as they look at her. She gives him a quirk of the mouth that doesn't quite become a smile, and he nods, saying he understands, or at least he thinks he does.
He's still looking at her with those soft eyes and they are leaning into each other and her head is tilted up and his is ducked down and she wonders if maybe, despite the horrible timing and everything that's going on around them and what they are about to do, she wonders if he'll try to kiss her. She doesn't think she'll stop him if he does.
He still looking at her, unblinking and intense and leaning down some more. She thinks he really might do it, and, pulse thundering, she tilts her head back just a bit more, ready and open and -
There's a cough from somewhere behind and to the left of her. Stiles' head snaps up, and he's dropped her hand and a foot away from her before she can blink. She turns to look behind her, despite knowing a flush must be crawling up her neck. Isaac has a hand on the back of his neck, studying the floor (Lydia's quite sure he's the one that coughed), Allison and Scott both look like they would be smiling if she wasn't feeling so guilty and he hadn't just had his heart ripped out, and Deaton is watching them with a knowing gaze that isn't smiling but it isn't unhappy either.
Lydia's entire face is burning now, but she doesn't dare look behind her to see how Stiles is.
"Why don't we get this going? The sooner we do, the sooner we can start working to save your parents," Deaton says, and doesn't that sober them all up.
They fill the tubs (and she stares at the icy water, hating that Stiles is going to have to get in that, that Stiles is going to have to die in that, that she is going to have to help him die in that). They get in and she can't help but notice how Stiles forces himself all the way in without hesitation, despite the pain, while Scott and Allison sink in, inch by inch.
It's only after Stiles tells Scott his dad is in town and when Deaton tells her and Isaac that they must push down in thirty seconds, allowing everyone to brace themselves during the countdown, that Lydia speaks to Stiles for the first time since entering the room.
With her hands planted firmly on his shoulders, she leans down until her lips brush the shell of his ear and whispers, "We are going to save your father. I'm going to pull you back. I swear to you, Stiles, I'm going to bring you back."
He begins to shake harder than he already is as he opens his mouth to respond, whether to tell her that it's okay, she doesn't have to speak so gravely, or that he already knows she will, or maybe even that he loves her (and what she wouldn't give to hear those words now), but Deaton finishes his countdown and Lydia just repeats, "I swear," before pushing Stiles under.